A localized lump is a discrete, palpable mass confined to a specific anatomical area, arising from abnormal growth or swelling of tissue such as a cyst, abscess, lipoma, or neoplasm.

Localized Lump

Epidemiology and Risk Factors

The epidemiology of a localized lump depends entirely on the tissue of origin, site, and underlying pathology. However, some general principles apply:

The risk factors vary by site and tissue, but key themes recur:

Risk Factor Category	Examples	Mechanism
Age	↑ Age → ↑ risk of malignancy generally	Accumulation of somatic mutations over time
Sex	Male sex → thyroid nodules more likely malignant; Female → breast cancer	Hormonal and genetic differences
UV/radiation	Skin cancers (BCC, SCC, melanoma)	DNA damage (pyrimidine dimers), mutagenesis
Chronic irritation/inflammation	Marjolin's ulcer (SCC in chronic wound), scar cancer	Chronic regeneration → ↑ mitotic errors
Immunosuppression	Post-transplant → ↑ SCC, lymphoma, Kaposi sarcoma	Impaired immune surveillance
Genetic syndromes	Li-Fraumeni (TP53), FAP, MEN syndromes, BRCA1/2	Loss of tumour suppressor or gain-of-function oncogene
Chemical/toxin exposure	Asbestos (mesothelioma), arsenic (skin cancers)	Direct carcinogenesis
Hormonal	Estrogen exposure → breast cancer	Mitogenic effect on breast epithelium
Family history	1st-degree relative with same cancer → ↑ risk	Shared germline mutations + environment

Anatomy and Function Relevant to Localized Lumps

To properly assess a lump, you must understand the layered anatomy from superficial to deep. This dictates what the lump could be.

Epidermis → Dermis → Subcutaneous fat → Deep fascia → Muscle → Bone/Periosteum → Body cavity

Layer	Lumps Arising Here	Clinical Clue
Epidermis	Wart (verruca), seborrhoeic keratosis, SCC-in-situ (Bowen's)	Moves with skin, cannot pinch skin separately from lump
Dermis	Dermatofibroma, BCC, SCC, melanoma, intradermal naevus	Attached to overlying skin, moves with skin pinch
Subcutaneous	Lipoma, epidermoid cyst, sebaceous cyst, neurofibroma	Not attached to overlying skin in most cases ^[1]; moves freely over deep structures
Deep fascia	Ganglion cyst (arises from joint capsule/tendon sheath)	Fixed to deep structures but skin moves over it
Muscle	Intramuscular lipoma, desmoid tumour, sarcoma	Becomes more prominent on muscle contraction (if superficial to muscle) or less mobile/harder to feel (if within muscle — the muscle "grips" it)
Bone	Osteochondroma, giant cell tumour, bone cyst	Rock-hard, immobile, attached to bone
Vascular	Haemangioma, AV malformation, aneurysm	Pulsatile, compressible, may have bruit/thrill
Lymphatic	Lymphadenopathy, lymphoma	Discrete, rubbery; distribution follows lymphatic drainage

Why Does Muscle Contraction Help Localise a Lump?

If a lump is superficial to muscle, tensing the muscle pushes the lump forward → it becomes more prominent and more mobile. If the lump is within or deep to muscle, contraction of the muscle makes it less mobile or disappear — the muscle acts like a curtain being drawn over it. This is a classic examination trick.

Classification of Lumps by Pathological Nature

The causes of a localized lump can be systematized using a surgical sieve (the classic mnemonic for differential diagnosis). Here we focus on the etiology — i.e., what processes give rise to lumps:

A. Congenital / Developmental

Condition	Pathophysiology
Dermoid cyst	Cystic teratoma formed in-utero during embryonic fusion — contains developmentally mature tissues (skin, hair, fat, sweat glands, teeth) ^[3]. Located along fusion lines (lateral eyebrow, anterior fontanelle, midline). Implantation dermoids arise from penetrating injury driving epidermal fragments into dermis.
Thyroglossal duct cyst	Failure of obliteration of the thyroglossal duct (which the thyroid gland descends through from the foramen caecum of the tongue to the anterior neck). Cyst forms anywhere along this tract. Classic sign: moves upward on tongue protrusion (because of attachment to hyoid bone via the tract).
Branchial cyst	Arises from remnants of the 2nd branchial cleft/arch. Typically presents as a painless lump at the anterior border of sternocleidomastoid in young adults.
Preauricular sinus	Failure of fusion of the auricular hillocks during ear development → small pit anterior to the tragus.

B. Traumatic / Iatrogenic

Condition	Pathophysiology
Haematoma	Blunt or penetrating trauma → vessel rupture → blood collection in tissues. Initially soft, later becomes firm as it organises.
Fat necrosis	Ischaemic necrosis of fat lobules — usually follows trauma or breast reconstruction (flap ischaemia) ^[5]^[7]. Saponification of fat triggers chronic low-grade inflammation. Can mimic carcinoma clinically (painless lump ± skin dimpling, nipple retraction) and radiologically ^[5]^[7].
Implantation dermoid	Penetrating injury implants epidermal fragments into dermis → gradually forms a keratin-filled cyst ^[3]
Foreign body granuloma	Reaction to suture material, breast augmentation injections, splinters, etc.

C. Infective / Inflammatory

Condition	Pathophysiology
Abscess	Collection of pus within dermis or subcutaneous space ^[3]. Most commonly due to S. aureus (75%) ^[3]. Disruption of skin barrier allows bacterial entry → neutrophilic infiltration → tissue necrosis → walled-off pus collection. Clinically: painful, fluctuant, erythematous nodule ± surrounding cellulitis ^[3].
Cellulitis	Inflammation of deeper dermis + subcutaneous fat due to bacterial infection (β-haemolytic strep commonest, then S. aureus) ^[3]. Not truly a "lump" but can present as a diffuse, tender, indurated swelling.
Mastitis	Infection of breast tissue, mostly due to S. aureus ^[5]. Commonest in lactational setting (1st child). Stasis of milk → bacterial colonisation → infection. Can progress to abscess (fluctuant mass, fever) ^[5].
Reactive lymphadenopathy	Infection in drainage territory → antigen presentation in regional lymph node → follicular hyperplasia → palpable, tender, enlarged node.
Tuberculous lymphadenitis	Particularly important in Hong Kong — TB remains endemic. Presents as chronic, non-tender cervical lymphadenopathy ("cold abscess"), matted nodes, may form sinuses.
Pilonidal sinus	Infection & obstruction of hair follicle in intergluteal cleft → foreign body-type reaction → cavity formation ^[8]. RF: **Caucasian male with coarse dark body hair (rare in HK), prolonged sitting, increased sweating** ^[8].

D. Neoplastic

This is the largest and most clinically important category. We subdivide into benign and malignant:

Benign Neoplasms

Condition	Key Features	Pathophysiology
Lipoma	Most common benign soft-tissue neoplasm ^[1]^[2]. Soft, mobile, +ve slip sign ^[2], not attached to overlying skin ^[1]. Slow growing, never regress, rarely undergo malignant transformation into liposarcoma ^[2].	Mature enlarged fat cells without atypia ^[2] enclosed by thin fibrous capsule that have become overactive and distended with fat ^[1].
Epidermoid cyst (sebaceous cyst)	Most common cutaneous cyst. Has a punctum (tiny central pore). Contains keratin (cheesy, foul-smelling material).	Obstruction of hair follicle infundibulum → keratin accumulates within a cyst lined by stratified squamous epithelium. Despite the traditional name "sebaceous cyst," it does NOT arise from sebaceous glands.
Fibroadenoma	Most common benign breast tumour ^[5]. Well-defined rubbery mass, highly mobile ("breast mouse"), can be multiple & bilateral ^[5]. Reproductive age.	Proliferation of stromal & epithelial tissue of duct lobules ^[5]. Oestrogen-responsive — may enlarge during pregnancy and regress after menopause.
Intraductal papilloma	Benign breast lesion in perimenopausal women ^[5]. Presents with nipple discharge (bloody) ^[5].	Papillary proliferation within a breast duct, usually in a major subareolar duct. Friable papillary fronds bleed easily → bloody nipple discharge. Multiple papillomas: increased risk of CA ^[5].
Neurofibroma	Soft, pedunculated or sessile skin nodule. Button-hole sign (can be invaginated into subcutaneous tissue). Associated with NF1 (if multiple).	Proliferation of Schwann cells, fibroblasts, and perineural cells within peripheral nerve sheath.
Skin tag (acrochordon)	~50% of adults ^[3]. At sites of friction (axilla, neck, inframammary, inguinal) ^[3]. Pedunculated skin-colored lesions on narrow stalks ^[3].	Outgrowth of normal skin ^[3]. Associated with obesity, diabetes mellitus, ↑ age, pregnancy ^[3].
Ganglion cyst	Most common soft tissue tumour of the hand/wrist. Firm, transilluminant. Most commonly dorsal wrist (70%).	Mucinous degeneration of connective tissue adjacent to joint capsule or tendon sheath → accumulation of viscous fluid within a cyst.
Hepatic haemangioma	Most common benign liver tumour (3–20% population) ^[9]. Usually asymptomatic, found incidentally ^[9].	Congenital vascular malformation, enlarges by ectasia (not hyperplastic) ^[9].

Malignant Neoplasms

Condition	Key Features	Pathophysiology
Basal cell carcinoma	Most common skin cancer in Chinese ^[3]. 70% occur on the face (above earlobe–mouth corner line) ^[3]. Nodular (80%): pigmented nodule with telangiectasiae ± central ulceration → rodent ulcer ^[3]. Pigmented nodule common in Asians ^[3].	Arises from basal layer keratinocytes. UV-induced mutations in the Hedgehog signalling pathway (PTCH1 tumour suppressor). Locally invasive but almost never metastasizes.
Squamous cell carcinoma (SCC)	More rapid growth, everted edge, contact bleeding, ± lymph node involvement ^[3]. Can arise from premalignant lesions (actinic keratosis, Bowen's disease).	Malignant proliferation of keratinocytes. UV radiation → TP53 mutations → uncontrolled proliferation. Can metastasize to regional lymph nodes.
Melanoma	ABCDE criteria for suspicious moles. Subtypes: superficial spreading (most common overall), nodular, lentigo maligna, acral lentiginous (most common in dark-skinned individuals) ^[1].	Malignant transformation of melanocytes. UV radiation → BRAF (V600E) or NRAS mutations → uncontrolled melanocyte proliferation. Vertical growth phase = capacity for metastasis.
Breast carcinoma	Breast mass: hard, irregular, fixed, non-tender, mostly at upper outer quadrant ^[5]^[6]. Nipple discharge (unilateral, single duct, bloody = ↑ risk) ^[5]^[6]. Skin: dimpling, peau d'orange, ulceration ^[5]^[6].	Invasive ductal carcinoma (76% — most common) ^[5]. Malignant epithelial cells invade through basement membrane → spread via lymphatics (axillary nodes) and haematogenously. Peau d'orange = tumour invades dermal lymphatics → lymphatic obstruction → skin oedema tethered at hair follicle openings.
Thyroid carcinoma	Palpable neck lump, rapidly enlarging → pain, hoarseness, stridor ^[4]^[10]. Papillary (85%) — most common, spreads via lymphatics (compartment VI first) ^[10].	Depends on subtype. Papillary: RET/PTC rearrangements, BRAF V600E. Follicular: RAS mutations, PAX8-PPARγ. Medullary: RET proto-oncogene mutation ^[10], arises from parafollicular C cells ^[10].
Phyllodes tumour	Fibroepithelial tumour in older age (>40) ^[5]. Smooth painless mass, mobile. Can be malignant (metastasize via blood — ALND not required) ^[5].	Stromal hypercellularity ± atypia. Classified as benign, borderline, or malignant based on stromal features. Unlike carcinoma, spreads haematogenously (not lymphatically).
Soft tissue sarcoma	Deep, firm, enlarging, painless mass. > 5 cm, deep to fascia, rapid growth = red flags.	Malignant mesenchymal cells. Multiple genetic drivers (e.g., MDM2 amplification in liposarcoma, SYT-SSX fusion in synovial sarcoma).
Lymphoma	Painless, rubbery lymphadenopathy. "B symptoms" (fever, night sweats, > 10% weight loss).	Malignant proliferation of lymphoid cells. Hodgkin: Reed-Sternberg cells. Non-Hodgkin: various B-cell or T-cell lineages.

E. Vascular

Condition	Pathophysiology
Haemangioma (infantile)	Benign endothelial cell proliferation → rapid growth phase (first year of life) → gradual involution. Most common tumour of infancy.
Arteriovenous malformation	Congenital abnormal connection between arteries and veins → high-flow lesion. Pulsatile, may have bruit/thrill.
Femoral artery aneurysm	Localised dilation of common femoral artery (> 1.5× normal diameter). Pulsatile, expansile mass in groin.
Saphenous varix	Dilation of the proximal long saphenous vein near the saphenofemoral junction. Soft, compressible, has a cough impulse (like hernia). Disappears on lying down. Blue tinge. Differentiating feature from hernia: thrill on cough rather than just an impulse.

F. Degenerative / Metabolic

Condition	Pathophysiology
Ganglion	Mucinous degeneration of periarticular connective tissue
Gouty tophus	Deposition of monosodium urate crystals in soft tissues (ear helix, fingers, toes, olecranon) in chronic gout
Xanthoma	Lipid-laden macrophage deposition in skin/tendons in hyperlipidaemia
Calcinosis	Calcium deposition in soft tissues (seen in scleroderma — CREST syndrome, dermatomyositis)

G. Lymphatic Obstruction

Condition	Pathophysiology
Lymphoedema	Obstruction of lymphatic drainage → oedema with high protein content ^[11]. Primary (Milroy's, Meige) or Secondary (filariasis — MC worldwide; malignancy — MC in developed countries) ^[11]. Clinically: pitting oedema initially → warty & thickened skin ^[11]. Stemmer sign: unable to lift skin of 2nd finger/toe ^[11].

Hong Kong Focus

In Hong Kong, pay special attention to:

Nasopharyngeal carcinoma (NPC) presenting as a neck lump (cervical lymphadenopathy as first presentation in up to 40%)
TB lymphadenitis — still prevalent
Hepatocellular carcinoma — high hepatitis B prevalence → liver masses
Thyroid nodules/cancer — thyroid cancer incidence is rising in HK, especially papillary type
Breast carcinoma — 1st in incidence in HK females, median age 55 (younger than global data), lifetime risk 1:16 ^[5]^[6]
Lung cancer — 1st in mortality in HK ^[12]

Relevant Classification Systems

The surgical sieve is the standard framework — use the mnemonic VITAMIN CD:

Letter	Category	Example
V	Vascular	Aneurysm, haemangioma, varix
I	Infective/Inflammatory	Abscess, reactive LN, TB
T	Traumatic	Haematoma, fat necrosis
A	Autoimmune	Rheumatoid nodule, gouty tophus
M	Metabolic	Xanthoma, calcinosis
I	Iatrogenic	Post-surgical seroma, implant reaction
N	Neoplastic (benign/malignant)	Lipoma, carcinoma, sarcoma
C	Congenital	Dermoid cyst, branchial cyst
D	Degenerative	Ganglion, Baker's cyst

This is the most practical bedside approach:

Site	Common Lumps
Scalp	Sebaceous cyst, lipoma, dermoid, BCC/SCC, pilar cyst
Face	BCC (medial canthus), SCC, sebaceous cyst, parotid tumour
Anterior neck	Thyroid enlargement, lymphadenopathy, skin lumps, branchial cyst, thyroglossal duct cyst ^[4]
Posterior triangle of neck	Lymph node (think NPC in HK!), cystic hygroma (children)
Breast	Fibroadenoma, cyst, carcinoma, phyllodes, fat necrosis ^[5]
Axilla	Lymph node, lipoma, hidradenitis suppurativa abscess
Groin	Inguinal hernia, femoral hernia, femoral artery aneurysm, saphenous varix, inguinal lymph node, lymphoma, lipoma, abscess, undescended testis, hydrocele ^[1]
Limbs	Lipoma, ganglion, neurofibroma, sarcoma
Perianal	Perianal abscess, skin tag, pilonidal sinus ^[8], haemorrhoids, anal carcinoma ^[8]

This is the most important clinical distinction when assessing any lump:

Feature	Benign	Malignant
Growth rate	Slow, stable	Rapid or relentless
Border	Well-defined, smooth	Irregular, poorly defined
Surface	Smooth	Nodular, irregular
Consistency	Soft or rubbery	Hard ("stony hard")
Tenderness	May be tender	Usually non-tender (exception: inflammatory carcinoma)
Mobility	Freely mobile	Fixed to skin, muscle, or bone
Skin changes	None	Tethering, dimpling, peau d'orange, ulceration
Lymph nodes	Not involved	Regional lymphadenopathy
Number	Often solitary (but lipomas/neurofibromas can be multiple)	Solitary or multiple (metastatic)

The 'Red Flag' Features of a Malignant Lump — Must Know!

Remember these features that should raise suspicion for malignancy:

Rapid growth (weeks to months)
Hard, irregular, non-tender
Fixed (to skin, deep structures, or both)
Overlying skin changes (ulceration, dimpling, peau d'orange, satellite nodules)
Regional lymphadenopathy (hard, non-tender, fixed nodes)
Size > 5 cm (especially for soft tissue masses → think sarcoma)
Deep to deep fascia (for limb lumps → sarcoma until proven otherwise)
Constitutional symptoms (weight loss, fever, night sweats)

Clinical Features

A. History (Symptoms)

The history of a localized lump follows a systematic approach. Think of it as answering: "What is this lump, and is it dangerous?"

Question	Rationale / Pathophysiological Basis
Onset: When did you first notice it? Sudden or gradual?	Sudden onset → haematoma, abscess, cyst rupture. Gradual → neoplasm, cyst. Sudden ↑ size: anaplastic carcinoma, primary lymphoma, haemorrhage into necrotic nodule/cyst, subacute thyroiditis ^[4]
Duration: How long has it been there?	Long-standing (years) and stable → likely benign. Weeks to months and enlarging → concern for malignancy.
Growth pattern: Getting bigger, smaller, or staying the same?	Progressive growth over weeks-months, especially if firm/hard with fixation → malignant ^[4]. Fluctuating size → cyst (fills and empties) or inflammatory (waxes and wanes).
Pain/tenderness	Pain suggests inflammation, infection, nerve involvement, or haemorrhage into a lesion. Most malignant lumps are painless (exception: bone mets, inflammatory breast cancer). Pathophysiology: pain from stretching of capsule, pressure on nerves, or release of inflammatory mediators.
Change in overlying skin	Redness → inflammation/infection. Dimpling → tethering of Cooper's ligaments in breast (carcinoma pulling on ligamentous septae). Peau d'orange → dermal lymphatic obstruction by tumour. Ulceration → tumour outgrowing its blood supply or direct invasion through skin.
Cyclical changes	Important for breast lumps ^[6]: Cyclical mastalgia/nodularity → fibrocystic changes ^[5]. Non-cyclical, persistent mass → ↑ concern for carcinoma.
Discharge	Nipple discharge: colour? Consistency? ^[6]. Bloody, unilateral, single-duct → ↑ risk malignancy or intraductal papilloma ^[5]^[6]. Green/yellow → duct ectasia. Milky → galactorrhoea (prolactinoma, drugs). Wound discharge → infected cyst, abscess.
Number: Is this the only one? Any others?	Multiple lipomas → familial lipomatosis, Dercum's disease, Madelung's disease ^[1]^[2]. Multiple lymph nodes → lymphoma, metastatic disease, systemic infection. Contralateral breast lump: bilateral primary breast carcinoma common ^[6].

Symptom	Pathophysiological Basis
Constitutional symptoms: loss of appetite, loss of weight ^[6]	Malignancy → production of cytokines (TNF-α, IL-6) → cancer cachexia. Rarely found in early cancers ^[6].
Fever	Infection (abscess, cellulitis). Lymphoma (B symptoms). Inflammatory breast cancer.
Metastatic symptoms: bone pain, SOB, epigastric discomfort ^[6]	Bone metastases → stretching of periosteum → pain. Lung/pleural mets → effusion → SOB. Liver mets → capsular stretch → RUQ/epigastric discomfort. Generally come earlier than constitutional symptoms ^[6].
Compressive symptoms: dyspnoea, dysphagia, dysphonia ^[4]	For neck lumps — indicates rapid growth with invasion ^[4]. Dyspnoea = tracheal compression. Dysphagia = oesophageal compression. Dysphonia = recurrent laryngeal nerve (RLN) palsy ^[4].
Thyrotoxic/hypothyroid symptoms ^[4]	If the lump is thyroid: Hyperthyroid: hyperactive, irritable, weight loss despite ↑ appetite, heat intolerance, ↑ sweating, diarrhoea, palpitations, tremor ^[4]. Hypothyroid: fatigue, weight gain but ↓ appetite, cold intolerance, constipation, bradycardia ^[4].
Skin-related symptoms	Itch → dermatitis (Paget's disease of nipple), eczema. Pigment change → melanoma.

B. Physical Examination (Signs)

The examination of a lump is one of the most structured clinical skills in surgery. The approach is inspection → palpation → special tests → regional examination → systemic examination.

Feature	What to Look For	Pathophysiological Basis
Site	Anatomical region dictates differential	Structures present at that site (see anatomy section)
Size	Estimate in cm (two dimensions)	> 5 cm soft tissue mass = sarcoma until proven otherwise
Shape	Round, oval, multilobulated, irregular	Regular shape → benign (e.g. lipoma); Irregular → malignant
Number	Solitary vs multiple	Multiple → metastatic, syndromic (NF1, lipomatosis), lymphoma
Colour	Skin-coloured, red, blue/purple, pigmented	Red → inflamed/vascular. Blue → vascular (varix, haemangioma). Pigmented → melanocytic or BCC (in Asians)
Skin changes	Ulceration, dimpling, peau d'orange ^[6]	Ulcer: tumour outgrows blood supply. Dimpling: Cooper's ligament tethering. Peau d'orange: dermal lymphatic blockage.
Surface	Smooth, lobulated, irregular	Smooth → cyst or benign neoplasm. Irregular → malignancy
Edge/margin	Well-defined vs ill-defined	Well-defined → benign. Ill-defined → malignant (infiltrative growth)
Nipple changes (for breast)	5D: deviation, discolouration, dermatitis, depression (retraction), discharge ^[6]	Retraction: tumour pulls on subareolar ducts. Dermatitis: Paget's disease (intraepidermal spread of ductal carcinoma cells).
Scars	Previous surgery	Previous excision, lymph node biopsy ^[6]
Special features	Punctum (epidermoid cyst), sinus/pit (dermoid, pilonidal), pedunculated stalk (skin tag)	Punctum = blocked hair follicle infundibulum. Sinus = abnormal tract connecting cavity to surface.

Feature	Technique	Pathophysiological Basis
Temperature	Dorsum of hand over lump	Warm → inflammation, infection, or highly vascular tumour
Tenderness	Gentle pressure	Tenderness → infection, inflammation, haemorrhage into cyst, nerve involvement
Consistency	Firm pressure, compare with known textures	Soft → lipoma (like normal fat), cyst. Firm/rubbery → fibroadenoma, lymph node. Hard → carcinoma, bone. Stony hard → calcified lesion, bone tumour. Fluctuant → fluid-filled (abscess, cyst).
Surface	Roll fingers over it	Smooth → benign. Nodular/irregular → malignant
Edge/margin	Try to get fingers around it	Well-defined → benign. Poorly-defined → malignant ^[4]
Mobility	Move lump in two planes; then tense underlying muscle and re-test	Freely mobile in all directions + slip sign → lipoma ^[2]. Mobile in all planes → subcutaneous. Fixed to skin: pinch skin — does it pucker? Carcinoma tethers to skin via Cooper's ligaments or direct invasion. Fixed to muscle: tense muscle — does mobility ↓? → deep invasion.
Fluctuance	Press on lump from one edge; feel at 90° for transmitted impulse	Positive = fluid-filled (cyst, abscess). Cross-fluctuance present in two perpendicular planes confirms fluid, not just soft tissue displacement.
Transillumination	Dark room, pen torch placed on one side	Positive (glowing red) → clear fluid (hydrocele, ganglion, cystic hygroma). Negative → solid or contains blood/pus.
Pulsatility	Palpate with fingertips	Pulsatile + expansile → aneurysm (true expansion in all directions). Transmitted pulsation → lump sits on a vessel but is not vascular itself.
Compressibility	Compress and release	Empties on compression, refills on release → vascular (venous malformation, varix, haemangioma).
Cough impulse	Ask patient to cough while palpating	Positive → hernia or saphenous varix. Cough → ↑ intra-abdominal pressure → impulse transmitted through defect (hernia) or incompetent valve (varix).
Reducibility	Gently press; does it go back?	Reducible → hernia (contents return to peritoneal cavity). Irreducible → incarcerated hernia, solid mass.
Auscultation	Stethoscope over lump	Bruit → AV malformation, aneurysm, vascular tumour. Bowel sounds → hernia containing bowel.

The Slip Sign — Pathognomonic for Lipoma

The slip sign (also called Cope's sign): when you press the edge of a lipoma, it slips away from under your fingers. This happens because the lipoma is a smooth, encapsulated mass of mature fat cells ^[2] sitting in loose subcutaneous tissue. It is freely mobile in all directions because it is not attached to surrounding structures by anything other than its thin fibrous capsule.

Site	Test	What It Tells You
Neck lump	Move on swallowing → thyroid or nearby structure moves with laryngeal elevator. Move on tongue protrusion → thyroglossal duct cyst (attached to hyoid via thyroglossal tract).	Swallowing → larynx moves up → pretracheal fascia encases thyroid → thyroid moves up. Tongue protrusion → hyoid is pulled up by geniohyoid/hyoglossus → thyroglossal cyst moves up.
Breast	Palpation: start from normal side. Comment on: site, size, shape, border, surface, consistency, tenderness, mobility (skin & muscle). Include axillary tail. ^[6]	Systematic approach ensures no pathology is missed. Testing fixation to pectoralis (tense the muscle by pressing hands on hips).
Axillary LN	Groups: anterior, posterior, medial, lateral, apical. Comment: number, site, size, consistency, tenderness, fixation ^[6]	Axillary lymph nodes drain the breast, upper limb, and chest wall. Matted/fixed nodes suggest malignant infiltration.
Groin	Get above it → can you get above the lump? No → inguinal hernia (extends from above inguinal canal). Yes → femoral hernia, lymph node, etc.	The inguinal canal passes through the abdominal wall above the inguinal ligament. A hernia emerges from within it → you cannot palpate above it. A lymph node or femoral hernia sits below the inguinal ligament → you can get above it.
Limb	Test mobility with joint in different positions. Tense overlying muscle.	Ganglion: less mobile when tendons taut. Sarcoma: less mobile when overlying muscle contracted (if intramuscular/deep).

Always examine the regional lymph nodes draining the area of the lump — this is essential for cancer staging:

Lump Site	Regional Lymph Nodes
Scalp/face	Pre-auricular, post-auricular, submental, submandibular, cervical chain
Neck/thyroid	Cervical nodes (levels I–VI), supraclavicular
Breast	Axillary (anterior, posterior, medial, lateral, apical), supraclavicular, internal mammary
Upper limb	Epitrochlear, axillary
Lower limb	Popliteal, inguinal
Groin	Inguinal, iliac
Perianal	Inguinal (below dentate line → superficial inguinal via pudendal drainage)

High Yield Summary

Key Points for Exam:

Systematic approach to any lump: History → Inspection → Palpation → Special tests → Regional LN → Systemic
Lipoma = most common benign soft tissue neoplasm — soft, mobile, slip sign positive, subcutaneous, not attached to skin
BCC = most common skin cancer in Chinese — face (medial canthus), pigmented in Asians, rodent ulcer, locally invasive but almost never metastasizes
Fibroadenoma = most common benign breast tumour — rubbery, highly mobile "breast mouse", reproductive age
Benign vs malignant features: Benign = well-defined, smooth, soft/rubbery, mobile, slow-growing. Malignant = hard, irregular, fixed, non-tender, rapid growth, skin changes, LN involvement
Red flags: rapid growth, > 5 cm, deep to fascia, hard/irregular, fixed, skin changes (dimpling, peau d'orange, ulceration), LN, constitutional symptoms
Breast triple assessment: clinical + radiological + pathological — must know for exam
Breast risk factors: ↑ oestrogen (early menarche, late menopause, nulliparity, no breastfeeding, COC/HRT), FHx (BRCA), previous breast pathology, radiation, lifestyle
Thyroid lump red flags for malignancy: male, age < 14 or > 70, solitary nodule, firm/hard, fixed, pressure symptoms/RLN palsy, cervical LN, neck irradiation, FHx thyroid CA
Layer determines differential: always think which tissue layer the lump arises from based on mobility testing
For neck lumps, DDx includes: thyroid enlargement, lymphadenopathy, skin lumps, branchial cyst, thyroglossal duct cyst
Fat necrosis can mimic breast carcinoma clinically AND radiologically — always ask about trauma history or breast procedures

Active Recall - Localized Lump

Differential Diagnosis of a Localized Lump

The differential diagnosis (DDx) of a localized lump is arguably one of the broadest in all of surgery. The key to narrowing it down is a structured, layered approach: you use the site, the tissue layer of origin, and the clinical characteristics to whittle a huge list into a handful of likely diagnoses.

Think of it this way: the history and examination you performed in the previous section aren't just descriptive — they are diagnostic tools. Every feature you elicited (site, consistency, mobility, skin attachment, transillumination, cough impulse, etc.) is now used to differentiate one lump from another.

The single most useful framework is to think "which tissue layer does this lump arise from?" — because each layer has its own set of pathologies. The examination findings tell you the layer; the layer tells you the differential.

Layer	Benign	Malignant
Epidermis	Papilloma, viral warts, seborrhoeic keratosis, keratoacanthoma	Bowen's disease (SCC-in-situ), squamous cell carcinoma, basal cell carcinoma
Dermis	Sebaceous cyst (epidermoid cyst), acrochordon (skin tag), neurofibroma, dermatofibroma	Dermatofibrosarcoma protuberans
Subcutaneous tissue	Lipoma, angiolipoma, dermoid cyst, ganglion cyst	Liposarcoma
Bone	Osteoma	Osteosarcoma, bone metastasis
Melanocytes	Pigmented naevus (moles)	Malignant melanoma
Vascular	Pyogenic granuloma, cherry angioma (Campbell de Morgan spot)	Angiosarcoma, Kaposi sarcoma
Nerves	Glioma (peripheral), schwannoma	Malignant peripheral nerve sheath tumour

^[1]^[2]

This table is your mental scaffold. When you see a lump, ask yourself: "Is this epidermal, dermal, subcutaneous, or deeper?" — then run through the relevant column.

Why Layer Matters More Than Anything Else

A lipoma is subcutaneous → it is NOT attached to overlying skin and you can pinch the skin separately from it. An epidermoid cyst is dermal → it IS attached to the skin and moves with it. A dermatofibroma is dermal → it dimples when pinched (buttonhole sign) because it is tethered into the dermis. These are not random exam findings — they are direct consequences of which layer the lump arises from. Always determine the layer first.

Site-Specific Differentials

While the layer-based approach works for any lump, certain anatomical sites have their own characteristic differential lists that you must know cold. Let's go through the high-yield ones.

D/dx of anterior neck lump: ^[3]

Thyroid enlargement (diffuse = Graves'/Hashimoto's/multinodular goitre; focal = solitary nodule/cyst/carcinoma)
Lymphadenopathy (reactive, TB, lymphoma, metastatic — in HK always think NPC)
Skin lumps and bumps (lipoma, sebaceous cyst, dermoid)
Branchial cyst (if paediatric) — anterior to SCM, fluctuant, transilluminant
Thyroglossal duct cyst (if paediatric) — midline, moves on swallowing AND tongue protrusion

How do you differentiate?

Feature	Thyroid	Thyroglossal Cyst	Branchial Cyst	Lymph Node
Position	Central/lateral neck, overlying thyroid	Midline, at or below hyoid	Anterior border of SCM	Variable; follows nodal stations
Moves on swallowing	Yes (pretracheal fascia)	Yes (attached to hyoid)	No	No
Moves on tongue protrusion	No	Yes (thyroglossal duct connects foramen caecum → hyoid → thyroid)	No	No
Consistency	Firm (nodule) or diffuse (goitre)	Smooth, cystic	Smooth, cystic	Rubbery (lymphoma), hard (metastatic), soft (reactive)
Transillumination	Negative (solid)	Positive (fluid)	Positive (fluid)	Negative
Age	Any age	Children/young adults	Late childhood/young adults	Any

Why does a thyroglossal cyst move on tongue protrusion? The thyroglossal duct runs from the foramen caecum of the tongue → through or near the hyoid bone → to the thyroid's final position. Even after the duct obliterates, a cyst along this tract retains a fibrous attachment to the hyoid. When you protrude the tongue, the genioglossus and hyoglossus muscles pull the hyoid upward and forward → the cyst is dragged with it. A thyroid lump does NOT do this because it has no attachment to the hyoid.

This is a classic exam favourite. The key structures passing through the groin are: inguinal canal, femoral vessels, saphenous vein, lymph nodes, and the spermatic cord.

Classification	Differential	Key Distinguishing Feature
Hernia	Inguinal hernia	Cough impulse +ve, cannot get above it, reducible (if not incarcerated)
	Femoral hernia	Below and lateral to pubic tubercle, more common in females, cannot reduce easily
Vascular	Femoral artery aneurysm	Pulsatile AND expansile (expands in all directions with each pulse)
	Saphenous varix	Soft, compressible, disappears on lying down, blue tinge, thrill on cough (not just impulse)
Lymphatics	Inguinal lymph node	Discrete, firm/rubbery, non-pulsatile, non-reducible. Reactive (tender, soft) vs metastatic (hard, fixed) vs lymphoma (rubbery, non-tender)
	Lymphoma	Rubbery, non-tender, may be multiple, ± B symptoms
Nerves	Neuroma	Tender on palpation, Tinel sign +ve, along nerve distribution
Soft tissues	Lipoma	Soft, slip sign +ve, mobile, not attached to skin
	Abscess	Hot, tender, fluctuant, erythematous, ± cellulitis
Others	Undescended testis	Empty ipsilateral scrotum, lump in inguinal canal
	Communicating hydrocele (males)	Transilluminant, fluctuant, can get above it (cf. inguinal hernia you cannot) — but increases in size during the day
	Hydrocele of spermatic cord (males)	Encysted, transilluminant, within inguinal canal
	Hydrocele of canal of Nuck (females)	Female equivalent of encysted hydrocele of cord

^[1]

Why can you "get above" a femoral hernia but not an inguinal hernia? An inguinal hernia emerges from the deep inguinal ring, which is above the inguinal ligament, inside the abdominopelvic cavity — so you physically cannot place your examining fingers above the lump's origin. A femoral hernia emerges through the femoral canal, which is below the inguinal ligament — the inguinal ligament itself separates you from the abdominal cavity, so you CAN palpate above the lump. The same applies to lymph nodes, saphenous varix, etc.

How do you tell a saphenous varix from a femoral hernia? Both have a cough impulse. But a varix has a thrill on coughing (because of turbulent venous blood flow through the incompetent saphenofemoral junction), disappears completely on lying down (venous drainage empties it), and has a bluish colour. A hernia has an impulse on coughing but no thrill, may or may not reduce on lying down, and is not blue.

Triple assessment (clinical + radiological + pathological) is the gold standard approach for any breast lump ^[4]^[5]. But clinically, the differential is narrowed by age and lump characteristics:

Condition	Age	Consistency	Mobility	Pain	Key Feature
Fibroadenoma	Reproductive age	Rubbery	Highly mobile ("breast mouse")	Painless	Well-defined, can be multiple & bilateral ^[4]
Breast cyst	Young female (or perimenopausal)	Soft & fluctuant	Mobile	± tender	USG: fluid-filled. Aspiration diagnostic and therapeutic ^[4]
Fibrocystic changes (most common benign breast disorder)	Young female	Nodular	Variable	Cyclical painful mass/nodularity	Serosanguinous nipple discharge, related to menstrual cycle ^[4]
Fat necrosis	Any	Firm	May be tethered	Usually painless	History of trauma or breast reconstruction. Mimics CA clinically & radiologically ^[4]
Breast carcinoma	Usually > 30y	Hard	Fixed (to skin or muscle)	Non-tender	Irregular/nodular surface, poorly-defined edge, dimpling, peau d'orange ^[5]
Intraductal papilloma	Perimenopausal	May not be palpable	—	—	Bloody nipple discharge ^[4]
Phyllodes tumour	Older age (> 40)	Smooth, firm	Mobile	Painless	Can be malignant (haematogenous spread, ALND not required) ^[4]
Mastitis / breast abscess	Lactational, 1st child	Induration / fluctuant (abscess)	—	Tender	S. aureus, erythema, fever, purulent discharge ^[4]
Mondor's disease	Any	Cord-like	—	Chest pain	Palpable subcutaneous cord (superficial sclerosing thrombophlebitis of thoraco-epigastric vein) ^[4]

Why is the upper outer quadrant the most common site for breast carcinoma? Because it contains the largest volume of breast tissue (~50% of glandular tissue) and the axillary tail of Spence. More glandular tissue = more epithelial cells at risk of malignant transformation = higher probability of carcinoma developing there.

Fat Necrosis: The Great Mimicker

Fat necrosis can mimic breast carcinoma clinically (painless lump, skin dimpling, nipple retraction) AND radiologically (spiculated mass on mammogram) ^[4]^[5]. Students often forget to ask about a history of trauma or previous breast procedures — this is the key distinguishing question. Always biopsy to rule out carcinoma.

D. Differential Diagnosis of a Skin Lump/Ulcer

This overlaps heavily with the layer-based approach above, but here we focus on clinical differentiation of the most commonly confused lesions:

Feature	BCC	SCC	Keratoacanthoma	Melanoma
Growth rate	Slow (months-years)	More rapid growth ^[6]	Rapid (2–4 weeks growth, 2–3 months to regress) ^[2]	Variable; nodular melanoma can grow rapidly
Edge	Rolled (pearly) edge ^[6]	Everted edge ^[6]	Volcano-like with central crater	Irregular, asymmetric
Surface	Central ulceration (rodent ulcer) ^[6]	Hyperkeratotic or ulcerated, fleshy granulomatous base ^[6]	Central keratin-filled crater ^[2]	May be flat, raised, or ulcerated
Colour	Pigmented in Asians ^[6]; pearly/translucent in Caucasians	Red-brown	Skin-coloured, black necrotic core	Brown-black (or amelanotic — pink)
Bleeding	Less common	Contact bleeding (more common than BCC) ^[6]	Not typical	Can bleed if ulcerated
LN involvement	Almost never metastasizes	± LN ^[6]	No (benign, self-resolving)	Common in advanced disease
Spontaneous regression	No	No	Yes — characteristic ^[2]	No (except rare partial regression)
Key ddx for BCC	Keratoacanthoma, SCC, intradermal naevus, sebaceous cyst, melanoma (if pigmented) ^[6]
Key ddx for SCC		Keratoacanthoma, infected wart, actinic keratosis, pyogenic granuloma, amelanotic melanoma, BCC ^[6]

^[2]^[6]

Why does a keratoacanthoma regress spontaneously? It arises from the infundibulum of a hair follicle with rapid keratinocyte proliferation forming a dome with a central keratin plug. The leading theory is that immune recognition eventually triggers apoptosis and regression — the central keratin core separates and the lump collapses, leaving a depressed scar ^[2]. However, because clinical and histopathological features closely resemble SCC, you should ALWAYS suspect malignancy in keratoacanthoma ^[2] and excise for definitive histology.

Feature	Epidermoid Cyst	Lipoma	Dermoid Cyst	Dermatofibroma
Layer	Dermis	Subcutaneous	Subcutaneous (congenital) or dermis (implantation)	Dermis
Attached to skin	Yes — has a punctum	No — NOT attached to overlying skin ^[1]	Not attached to skin ^[7]	Fixed to subcutaneous tissue ^[8]
Consistency	Firm, slightly compressible	Soft	Rubbery, noncompressible ^[7]	Firm 'woody' consistency ^[8]
Mobility	Moves with skin	Mobile in all directions, +ve slip sign ^[9]	Limited	Limited (fixed deep)
Special sign	Punctum (blocked follicle ostium)	Slip sign	Dermal sinus (pit on overlying skin) ± tuft of hair ^[7]	Buttonhole sign (dimples when pinched) ^[8]
Transillumination	Negative	Negative	Negative	Negative
Contents	Keratin (cheesy, foul-smelling)	Mature fat cells	Mixed tissues (skin, hair, fat, teeth)	Fibroblastic tissue

Why does a dermatofibroma dimple when pinched (buttonhole sign)? The dermatofibroma is a benign dermal proliferation of fibroblasts ^[8] that is tethered to the subcutaneous tissue below it. When you pinch the overlying skin, the skin is lifted but the tethered lesion cannot rise — so the skin dimples inward over the fixed lesion, creating the characteristic "buttonhole" or dimple sign.

Feature	Lipoma	Ganglion	Sebaceous Cyst	Abscess
Site	Shoulder, neck, trunk, UL ^[9]	Dorsal wrist (70%) ^[10]	Hair-bearing areas (scalp, face, trunk)	Anywhere, especially friction sites
Consistency	Soft	Firm, rubbery ^[10]	Firm	Fluctuant
Transillumination	Negative	Positive ^[10] (contains gelatinous fluid)	Negative	Negative (pus is opaque)
Tenderness	Non-tender	Usually non-tender (unless nerve compression)	Non-tender unless infected	Tender, warm, erythematous
Mobility	Mobile in all directions	Attached to joint capsule/tendon sheath → limited ^[10]	Attached to skin (punctum)	Fixed (surrounded by inflammation)
Key feature	Slip sign	Location near joint; never becomes malignant ^[10]	Punctum; cheesy discharge if ruptures	Fever, surrounding cellulitis

Lymph nodes can present as lumps anywhere along the lymphatic chain. The clinical features of the node itself help narrow the differential:

Feature	Reactive/Infective	TB	Lymphoma	Metastatic Carcinoma
Consistency	Soft ^[11]	Firm initially → caseous ("cold abscess")	Firm, rubbery ^[11]	Hard ^[11]
Tenderness	Tender	Non-tender (cold abscess)	Non-tender	Non-tender
Matting	No	Yes (perinodal caseation)	Sometimes	Sometimes (perinodal invasion)
Fixation	Mobile	May be fixed (matted)	Mobile or fixed	Fixed (invasion beyond capsule)
Distribution	Draining infection territory	Cervical (in HK — think TB); can be any	Generalised or localised	Draining the primary tumour site
Systemic features	Fever, local infection signs	Fever, night sweats, weight loss (TB constitutional symptoms)	B symptoms: fever, drenching night sweats, > 10% weight loss in 6 months	Symptoms of primary malignancy
Biopsy	Not usually needed	Caseating granulomas, AFB on ZN stain	Excisional biopsy required (FNAC useless — architectural detail needed) ^[11]	FNAC/core biopsy often sufficient

^[11]

FNAC is Useless for Lymphoma!

FNAC provides cytological information only — it is useless in lymphoma because lymphoma diagnosis requires architectural detail (e.g., nodular vs diffuse pattern, Reed-Sternberg cells in Hodgkin's). Excisional biopsy is the mode of choice when suspecting lymphoma ^[11]. Core-needle or incisional biopsy is second-line (only if excision not feasible).

Feature	Haemangioma (infantile)	Pyogenic Granuloma	Cherry Angioma	AV Malformation	Aneurysm
Age	Infancy (grows, then involutes)	Any age (peak 20–30y or pregnancy) ^[12]	Usually > 30y, more common in elderly ^[12]	Congenital (may present later)	Older adults
Growth	Rapid in first year, then involutes	Rapidly developing over a few weeks then stabilises ^[12]	Slow ^[12]	Gradual	Gradual
Appearance	Bright red, well-demarcated, raised	Bright red, dome-shaped, moist, glistening surface ^[12]	Deep red, smooth papules (1–4mm) ^[12]	Pulsatile, may have bruit	Pulsatile, expansile
Bleeding	Rarely	Bleeds easily upon minor trauma (friable) ^[12]	Not as friable but profuse bleed if rupture ^[12]	If eroded	Not usually
Compressibility	Yes	—	Blanch with pressure ^[12]	Yes	Partially
Number	Usually solitary	Usually solitary ^[12]	Usually multiple ^[12]	Usually solitary	Usually solitary
Key ddx of PG		SCC, BCC, amelanotic melanoma, bacillary angiomatosis ^[12]

Lumps That Can Mimic Carcinoma ("The Great Mimickers")

These conditions are high yield because misdiagnosis has serious consequences:

Condition	What It Mimics	How to Differentiate
Fat necrosis	Breast carcinoma (painless lump, dimpling, nipple retraction, spiculated mass on MMG) ^[4]^[5]	History of trauma or breast reconstruction ^[5]; biopsy to confirm
Keratoacanthoma	SCC (rapidly growing skin nodule) ^[2]	Spontaneous regression in 2–3 months, central keratin crater ^[2]; but always excise
Sclerosing adenosis / radial scars	Breast carcinoma ^[4]	Pathological diagnosis; can mimic CA ^[4] → core biopsy required
Fibrocystic changes	Breast carcinoma (nodularity)	Cyclical changes related to menstrual cycle ^[4]; usually bilateral, upper outer quadrant
Phyllodes tumour	Fibroadenoma	Older age (> 40), larger, more rapid growth; can be malignant ^[4]
Adenoma	Breast carcinoma	Older age; can mimic CA ^[4]; biopsy required
Tuberculosis (cold abscess)	Lymphoma or metastatic LN	Non-tender, matted LN, constitutional symptoms; AFB stain, culture, TB PCR

When faced with any lump, systematically ask yourself:

What site is it in? → Narrows to site-specific differentials
What layer does it arise from? → Epidermal, dermal, subcutaneous, deep (use mobility tests)
Is it solid or cystic? → Fluctuance, transillumination
Is it vascular? → Pulsatility, compressibility, bruit
Is it benign or malignant? → Growth rate, consistency, edge, fixation, skin changes, LN

High Yield Summary

Differential Diagnosis of Localized Lump — Key Exam Points:

Use the layer-based approach: the examination findings (mobility, skin attachment, buttonhole sign, slip sign, punctum) tell you which layer → which differential
Anterior neck lump DDx: thyroid enlargement, lymphadenopathy, skin lumps, branchial cyst, thyroglossal duct cyst ^[3]
Groin lump DDx: inguinal/femoral hernia, femoral artery aneurysm, saphenous varix, inguinal LN, lymphoma, lipoma, abscess, undescended testis, hydroceles ^[1]
Breast lump DDx: fibroadenoma (mobile, rubbery), cyst (fluctuant), fibrocystic changes (cyclical), fat necrosis (mimics CA), carcinoma (hard, fixed), intraductal papilloma (bloody discharge), phyllodes (> 40y, can be malignant)
BCC vs SCC vs keratoacanthoma: BCC = rolled edge, rodent ulcer, pigmented in Asians, rarely metastasises. SCC = everted edge, contact bleeding, ± LN. KA = volcano-like, central keratin crater, rapid growth then regression — but always excise to r/o SCC ^[6]
Fat necrosis and sclerosing adenosis mimic breast carcinoma clinically AND radiologically → must biopsy ^[4]
FNAC is useless for lymphoma — need excisional biopsy for architectural detail ^[11]
Lymph node consistency: Hard = solid malignancy. Firm/rubbery = lymphoma, chronic leukaemia. Soft = acute leukaemia, reactive ^[11]
Dermoid cyst DDx: sebaceous cyst (punctum), lipoma (softer, mobile), and site-dependent (pilonidal, thyroglossal, craniopharyngioma) ^[7]
Ganglion: most common soft tissue tumour of hands, dorsal wrist 70%, transilluminant, never becomes malignant ^[10]

Active Recall - Differential Diagnosis of Localized Lump

References

^[1] Senior notes: felixlai.md (Hernia section — DDx of groin mass) ^[2] Senior notes: felixlai.md (Lipoma section — DDx table by layer; Keratoacanthoma section) ^[3] Senior notes: Ryan Ho Endocrine.pdf (p18 — DDx of anterior neck lump) ^[4] Senior notes: maxim.md (Sections 8.3–8.6 — Breast assessment, inflammatory and non-inflammatory breast conditions, benign breast tumours) ^[5] Senior notes: Ryan Ho Urogenital.pdf (p200 — Fat necrosis; p205 — Carcinoma of breast) ^[6] Senior notes: Ryan Ho Rheumatology.pdf (pp187, 190 — SCC examination and BCC examination, DDx) ^[7] Senior notes: Ryan Ho Rheumatology.pdf (p168 — Dermoid cyst DDx) ^[8] Senior notes: Ryan Ho Rheumatology.pdf (p166 — Dermatofibroma) ^[9] Senior notes: Ryan Ho Rheumatology.pdf (p169 — Lipoma) ^[10] Senior notes: maxim.md (Ganglion cyst section); Senior notes: Ryan Ho Rheumatology.pdf (p173 — Ganglion) ^[11] Senior notes: Ryan Ho Haemtology.pdf (p87 — LN biopsy and consistency) ^[12] Senior notes: Ryan Ho Rheumatology.pdf (p178 — Pyogenic granuloma vs cherry angioma)

Standardised Reporting and Classification Systems

These systems exist to provide a common language for clinicians and radiologists to communicate the probability of malignancy. They are structured so that each category has a defined cancer risk and a recommended next step.

BI-RADS = Breast Imaging Reporting and Data System. Similar classifications exist for thyroid (TI-RADS), liver (LI-RADS), and prostate (PI-RADS) ^[13]^[14]

This is the most widely used classification for breast imaging and applies to mammography, ultrasound, AND MRI ^[13]^[14]:

BI-RADS Category	Description	Malignancy Risk	Recommended Action
0	Needs additional imaging evaluation	—	Further imaging
1	Negative imaging (no finding at all)	0%	Routine screening
2	Benign (0% risk)	0%	Routine screening
3	Probably benign (≤2%)	≤2%	F/U at 6/12
4	Suspicious (2–95%)	2–95%	Biopsy
	4A: low suspicion (2–10%)
	4B: moderate suspicion (10–50%)
	4C: high suspicion (50–95%)
5	Highly suggestive of malignancy (≥95%)	≥95%	Biopsy
6	Known (Bx-proven) malignancy	100%	Surgical excision

^[13]^[14]

Why does BI-RADS exist? Because imaging findings exist on a spectrum — a well-circumscribed oval lesion on mammogram is almost certainly benign, while a spiculated mass with microcalcifications is almost certainly malignant. BI-RADS standardises this so that every radiologist uses the same categories, and every surgeon knows exactly what next step is recommended. Without it, one radiologist might call a lesion "probably fine" and another "a bit suspicious" — BI-RADS eliminates this ambiguity.

USG of thyroid: look for features suggestive of malignancy (TI-RADS classification) → selective FNAC of those who have suspicious features ^[3]^[15]

The ACR TI-RADS (2017) assigns points for suspicious features on ultrasound. The total determines the TI-RADS category and whether FNAC is indicated:

Feature Category	Suspicious Finding	Points
Composition	Solid	2
Echogenicity	Hypoechoic, heterogeneous ^[3]	2–3
Shape	Taller than wide ^[3]	3
Margin	Irregular, lobulated, extrathyroidal extension	2–3
Echogenic foci	Microcalcification ( < 0.2 mm): represents the psammoma bodies of papillary CA ^[3]	3

TI-RADS Category	Description	FNAC Recommendation
TR1	Benign	No FNAC
TR2	Not suspicious	No FNAC
TR3	Mildly suspicious	FNAC if ≥ 2.5 cm (or follow-up if ≥ 1.5 cm)
TR4	Moderately suspicious	FNAC if ≥ 1.5 cm (or follow-up if ≥ 1.0 cm)
TR5	Highly suspicious	FNAC if ≥ 1.0 cm (or follow-up if ≥ 0.5 cm)

Once FNAC is performed on a thyroid nodule, the result is classified using the Bethesda system ^[16]:

Class	Diagnostic Category	Cancer Risk	Management
I	Non-diagnostic	1–4%	Repeat FNA
II	Benign	0–3%	Clinical follow-up
III	Atypia of undetermined significance (AUS) OR follicular lesion of undetermined significance (FLUS)	5–15%	Repeat FNA (or molecular testing)
IV	Follicular neoplasm	15–30%	Surgical lobectomy
V	Suspicious for malignancy	60–75%	Surgical lobectomy ± frozen section with total thyroidectomy
VI	Malignant	97–99%	Total thyroidectomy

^[16]

Why can't FNAC distinguish follicular adenoma from follicular carcinoma? Because the defining feature of follicular carcinoma is capsular or vascular invasion — this is an architectural feature you can only see on histology (the relationship between the tumour and its capsule). FNAC gives you individual cells, not architecture. So Bethesda IV ("follicular neoplasm") means "the cells look follicular, but I can't tell you if the capsule is invaded" → you need a lobectomy to examine the whole specimen histologically.

Apply the ABCDE system to a suspicious lesion: Asymmetry, Border, Colour, Diameter, Evolution and/or Elevation ^[17]

Letter	Feature	What It Means	Pathophysiological Basis
A	Asymmetry	One half does not match the other	Uncontrolled, disordered growth of different clones
B	Border	Irregular, ragged, notched, or blurred edges	Infiltrative growth pattern at tumour periphery
C	Colour	Variegated — multiple shades of brown, black, red, white, blue	Different clones of melanocytes producing different amounts of melanin ± regression (white) ± inflammation (red) ± deep melanin (blue)
D	Diameter	> 6 mm (larger than a pencil eraser)	Larger lesions have had more time to accumulate mutations
E	Evolution and/or Elevation	Any change in size, shape, colour, or symptoms over time	Active neoplastic growth; the most important criterion

^[17]

Evolution (E) is the Most Important Criterion

A lesion can be small, symmetric, and uniform in colour and still be a melanoma if it is changing. Conversely, many benign naevi are > 6 mm. The key question to ask patients is: "Has this mole changed recently?" — this single question captures the "E" and is the most sensitive clinical indicator. Key investigations for pigmented lesions include dermoscopy and excision biopsy ^[17].

Triple assessment: gold-standard for breast lump workup ^[13]^[14]

This is the single most important diagnostic framework for a breast lump. It combines three independent modalities, each with its own sensitivity, such that the overall sensitivity approaches 99.6% with a specificity of 93% ^[13]^[14]:

Component	Modality	Sensitivity
Clinical	History + Physical Examination	50–85%
Radiological	Mammogram ± USG ± MRI	~90%
Histopathological	FNAC or Core Biopsy	~91%

Regarded positive when any one is positive ^[13]^[14]

Why do we need all three? Because no single modality is perfect. Clinical examination misses small, deep, or non-palpable lesions. Imaging can be normal in dense breasts or with certain subtypes (e.g., lobular carcinoma on mammogram). Biopsy can give a false negative if the needle misses the lesion. By requiring concordance between all three — or acting on a positive result from any one — you minimise the chance of missing a cancer.

Investigation Modalities: Detailed Breakdown

A. Imaging

The workhorse of lump investigation. Cheap, non-invasive, no radiation, real-time, and can guide biopsy.

Principle: High-frequency sound waves (typically 7.5–15 MHz for superficial structures) are transmitted into tissue. Different tissues reflect sound differently → create an image based on echogenicity.

General Indications for Any Lump:

First-line for superficial soft tissue lumps (subcutaneous lipoma, cyst, lymph node)
First imaging study in young women or women who are pregnant or lactating ^[18] (avoids radiation, and dense young breast tissue makes mammogram less useful)
Diagnostic in palpable breast mass: D/dx between cystic vs solid masses ^[19]^[14]
Infected breast for any abscesses ^[19]
Axillary USG for any lymphadenopathy ^[19]
Image guidance for interventions: FNAB or core biopsy ^[19]
For all patients with goitre/palpable thyroid nodules ^[3]^[15] — NOT for screening test for healthy subjects (high sensitivity but low specificity) ^[3]^[15]
Lipoma: mainly by clinical exam ± USG to r/o other ddx ^[9]
Ganglion: clinical ± USG (well-defined margins, thick wall with acoustic enhancement) ^[10]

Breast USG — Key Findings:

Feature	Benign	Malignant
Shape	Wider-than-taller (ellipsoid)	Taller-than-wide ("fir-tree")
Margin	Smooth margins, macrolobulation	Spiculated or angular margins, microlobulation
Echogenicity	Hyperechogenicity, thin echogenic capsule	Hypoechogenicity
Calcification	Absent	Internal calcification, posterior acoustic shadowing
Vascularity	Absent	Central vascularity

^[18]

Why is "taller-than-wide" suspicious? A benign lesion grows within the tissue plane → it is wider than tall (compressed by adjacent tissue). A malignant lesion invades across tissue planes → it grows vertically as well as horizontally → appears taller than wide. This is a recurrent theme in both thyroid and breast ultrasonography because a taller-than-wide lesion suggests fascial invasion and inability to be compressed under USG ^[14].

Thyroid USG — Features Suggestive of Malignancy ^[3]^[15]:

The Nodule Itself	Surrounding Tissues
Echogenicity: hypoechoic, heterogeneous	Other nodules (likely MNG → reassuring)
Size/shape: taller than wide, irregular shape	Parenchymal abnormalities
Internal structure: solid or cystic with irregular septa	LNs: absent hilum, microcalcification, round, peripheral vascularity, hyperechoic — more likely to be malignant
Microcalcification ( < 0.2 mm): represents the psammoma bodies of papillary CA
Perilesional halo: absent or incomplete (represents compression of surrounding tissues w/o invasion)
Vascularity: intranodular vascularity
Local invasion: esp into strap muscles

^[3]^[15]

Most sensitive of all breast imaging modalities ^[13]^[14]

Principle: Low-dose X-ray of compressed breast tissue. Compression reduces overlapping tissue artefacts and lowers radiation dose.

Indications: Insensitive for young women (esp in Asians) — breast tissue in young and Asian women too dense → prefer USG ^[13]^[14]

> 40y if asymptomatic (for screening)
> 35y if symptomatic (for diagnosis)
Specimen mammogram for assessment of resection margin

^[13]^[14]

Standard Views:

Mediolateral oblique (MLO): captures the axillary tail ^[13]^[14] — any abnormality in the oblique milky way (tissue next to pectoralis muscle) is highly suggestive of carcinoma ^[13]
Craniocaudal (CC): note the upper lateral quadrant → > 50% of CA breast found there ^[13]^[14]
Compression (cone) view: focal compression onto suspicious areas → ↓ overlapping shadow → ↓ overlapping artefacts ^[13]

Reading a Mammogram ^[14]:

Finding	Benign Features	Malignant Features
Mass shape	Oval, round, well-circumscribed	Spiculated (~90% malignant)
Microcalcification	Scattered, tea cup/milk of calcium (round on CC, crescent on MLO — intracystic), larger, smooth, round, "popcorn" calcifications	Pleomorphic, clustered, segmental, linear branching pattern (following ductal drainage → suggestive of DCIS)
Other findings	—	Architectural distortion, skin thickening, nipple changes, axillary mass on MLO

^[14]

Why is a spiculated mass so suspicious? Spiculations are radiating lines extending from the mass into surrounding tissue. They represent desmoplastic reaction — the tumour invades and elicits fibroblast proliferation in surrounding stroma, creating these characteristic radiating strands. This is an imaging hallmark of invasive carcinoma.

Why does DCIS cause linear branching microcalcifications? DCIS grows within the ductal system. As the malignant cells undergo necrosis (especially in the comedo subtype), dystrophic calcification occurs within the necrotic debris. Because the disease follows the ductal anatomy, the calcifications arrange themselves in a linear branching pattern following the ductal drainage ^[14].

Principle: Cross-sectional X-ray imaging with computer reconstruction. Excellent for staging (detecting distant metastases) but not first-line for characterising superficial lumps.

Key Applications for Lumps:

Staging of proven malignancy: CT thorax/abdomen/pelvis (CT TAP) to detect metastatic disease
Thyroid: CT/MRI for retrosternal extension and staging (NOT routine) ^[3]^[15]. Note that the use of iodinated contrast may affect post-op radioactive iodine body scan ^[3]
Liver masses: Triphasic CT scan as 1st line for HCC diagnosis ^[21] — characteristic arterial enhancement → portal venous washout
Bone/soft tissue masses: to evaluate bone destruction, calcification patterns, soft tissue extent

CT Lesion Characteristics (general principles) ^[22]:

Shape	Significance
Round/oval	Slow, displacing growth pattern
Tubular	Vascular or neural
Wedge or triangular	Vascular territory (e.g. infarct)
Irregular or infiltrative	Malignancy

^[22]

B. Tissue Diagnosis (Biopsy)

The ultimate answer for any lump of uncertain nature is histopathology. The method of obtaining tissue depends on the clinical scenario.

Technique: 22–28G needle attached to syringe, multiple passes through the lump under suction. Yields individual cells (cytology), not tissue architecture.

FNAC vs Core Biopsy: nowadays often prefer upfront core Bx if suspicious of malignancy → FNAC reserved for those w/ low suspicion for malignancy ^[14]^[20]

	FNAC	Core Biopsy
Pros	Safe, simple, inexpensive, no LA required. Immediately distinguishes cysts from solid masses. Therapeutic for breast cysts	Can distinguish DCIS from invasive cancer. Allows IHC for ER, PR, HER2
Cons	Cannot reliably distinguish DCIS from invasive cancer. ↑ rate of FN or inadequate sample. IHC for hormonal status can be done by a cell block (but less reliable)	Can only be done in large masses ( > 2 cm). More invasive (9–18G needle vs 26–28G) → require LA + larger wound. ↑ pain and risk of complications
Findings	Ductal cells and stromal cells. Malignancy: ↑ N:C ratio, nuclear pleomorphism. Fibroadenoma: naked nucleus. Cysts: cystic fluid (send cytology if bloody to r/o intracystic CA). Infectious: polymorphs present	Tissue cores → full histological architecture

^[14]^[20]

When is FNAC Useless?

Lymphoma: FNAC provides only cytological information → useless in lymphoma ^[11] — need architectural detail (excisional biopsy). Follicular thyroid neoplasm: Cannot distinguish adenoma from carcinoma (need to see capsular/vascular invasion on histology). Hepatic haemangioma: FNAC contraindicated (risk of severe haemorrhage) ^[21].

Type	Description	Indication
Excisional Bx	Complete removal of lesion with margin	Diagnostic + therapeutic. Preferred for: suspected lymphoma (excisional biopsy is mode of choice) ^[11], small skin lesions (BCC, SCC), suspicious moles
Incisional Bx	Partial removal of a portion of the lesion	Large masses where complete excision is not practical initially (e.g., large sarcoma — to confirm diagnosis before definitive surgery)

Excision biopsy is key for pigmented lesions ^[17] — a suspicious pigmented lesion should be excised completely with a narrow margin (2 mm) for histological assessment of Breslow thickness, which determines further management.

Blood tests are adjunctive — they do not diagnose lumps directly but provide important contextual information:

Test	Indication	Interpretation
TFT (ultrasensitive TSH ± fT4)	All thyroid lumps ^[3]^[15]	Low TSH → hyperthyroidism (toxic nodule, Graves') → consider scintigraphy. High TSH → hypothyroidism (Hashimoto's).
Calcitonin	If history or clinical suspicion of familial medullary carcinoma or MEN2 ^[3]^[15]	Elevated → medullary thyroid carcinoma (C cell marker)
ESR, antithyroid antibodies (ATA)	Thyroiditis ^[3]^[15]	↑ ESR → subacute thyroiditis or malignancy. +ve anti-TPO/anti-Tg → Hashimoto's.
AFP	Suspected HCC (liver mass)	↑ in HCC (but also in cirrhosis, pregnancy, germ cell tumours)
LDH	Lymphoma, melanoma	Non-specific marker of tumour burden/cell turnover
FBC, CRP	Infectious causes (abscess, cellulitis)	Leucocytosis, raised CRP = active infection/inflammation
TPO, TSH receptor mRNA RT-PCR	As baseline tumour marker level if suspected or confirmed thyroid malignancy ^[3]^[15]	Baseline for post-op surveillance

Investigation	Indication	Key Findings
Direct laryngoscopy	For RLN palsy ^[3]^[15] in thyroid lumps	Vocal cord paralysis → invasion of recurrent laryngeal nerve by thyroid malignancy
Flow-volume loop study	For airway obstruction in obstructive/retrosternal goitre ^[3]^[15]	UAO results in a blunted flow-volume loop ^[3]^[15] — flattening of the inspiratory limb (variable extrathoracic) or both limbs (fixed obstruction)
CXR/CT/MRI thorax	Assessment of extent of retrosternal goitre ^[3]^[15]; staging for any malignancy	Tracheal deviation, mediastinal mass, lung metastases
Photography	To monitor dysplastic naevi ^[17]	Serial comparison to detect evolution (ABCDE "E")
OGD	Oesophageal involvement by thyroid malignancy ^[3]^[15]	Extrinsic compression or direct invasion
PET-CT	Staging of certain malignancies (lymphoma, melanoma, lung cancer)	↑ FDG uptake (SUVmax > 2.5) in metabolically active lesions ^[24]

Site-Specific Investigation Summaries

Step	Investigation	Key Points
1	Clinical examination	Sens 50–85% ^[13]
2	Imaging	If < 35y/pregnant → USG. If ≥ 35y → mammography + USG ^[13]^[14]. Apply BI-RADS.
3	MRI (if needed)	BRCA carriers, lobular CA, occult primary, neoadjuvant monitoring ^[14]^[20]
4	Biopsy	BI-RADS 4–5 → biopsy. Core Bx preferred if suspecting malignancy ^[14]^[20]
5	Staging (if malignant)	CT TAP, bone scan, PET-CT as indicated

Step	Investigation	Key Points
1	TFT: ultrasensitive TSH ± fT4 ^[3]^[15]	All patients
2	USG: routine for ALL goitre/nodules ^[3]^[15]	Apply TI-RADS
3	FNA cytology for suspicious nodules only ^[3]^[15]	Apply Bethesda system
4	Thyroid scintigraphy if nodule + ↓ TSH ^[3]^[15]	Hot = unlikely CA. Cold = consider FNA
5	Further Ix for obstructive/retrosternal goitre: CXR/CT/MRI thorax, flow-volume loop ^[3]^[15]
6	Calcitonin if Hx/suspicion of medullary CA/MEN2 ^[3]^[15]
7	Direct laryngoscopy for RLN palsy ^[3]^[15]

Step	Investigation	Key Points
1	Dermoscopy ^[17]	For all pigmented lesions
2	Photography ^[17]	To monitor dysplastic naevi
3	Excision biopsy ^[17]	For suspicious pigmented lesions — complete excision with margin
4	Punch/incisional biopsy	For non-pigmented skin cancers (BCC/SCC) — at ulcer edge ^[6]
5	Regional LN assessment	Palpation ± USG ± FNAC of enlarged nodes

High Yield Summary

Diagnostic Criteria and Investigation — Key Exam Points:

Triple assessment (clinical + radiological + histopathological) is the gold standard for breast lump workup — overall Sens 99.6%, Spec 93% — positive when ANY one is positive ^[13]^[14]
BI-RADS classification: 0 = more imaging, 1 = negative, 2 = benign, 3 = probably benign (F/U 6 mo), 4 = suspicious (Bx), 5 = highly suspicious (Bx), 6 = proven malignancy
Mammography: most sensitive breast imaging; use > 35–40y; insensitive in young/Asian dense breasts; spiculated mass (~90% malignant); linear branching microcalcifications suggest DCIS
Breast USG: first-line for < 35y/pregnant; taller-than-wide = suspicious; central vascularity = suspicious
MRI breast: highest sensitivity (88–100%) but low specificity; used for BRCA screening, lobular CA, occult primary, neoadjuvant monitoring
Core biopsy preferred over FNAC when suspecting malignancy — FNAC cannot distinguish DCIS from invasive CA, cannot do reliable IHC
Thyroid: TFT + USG for all → FNA of suspicious nodules (TI-RADS) → Bethesda classification → low TSH: scintigraphy first (hot = no FNA, cold = FNA)
Bethesda system: I = non-diagnostic (repeat), II = benign, III = AUS (repeat), IV = follicular neoplasm (lobectomy), V = suspicious (lobectomy ± total), VI = malignant (total thyroidectomy)
Pigmented lesions: ABCDE system + dermoscopy + excision biopsy; Evolution (E) is the most important criterion
FNAC is contraindicated in hepatic haemangioma (haemorrhage risk) and useless for lymphoma (no architecture)
Soft tissue mass red flags ( > 5 cm, deep to fascia, rapid growth) → urgent MRI + core biopsy → refer sarcoma MDT

Active Recall - Diagnostic Criteria and Investigations for Localized Lump

General Principles of Management

Management by Pathology Type

1. Benign Soft Tissue Lumps

Condition	Management	Rationale
Fibroadenoma	Observation. Surgical excision: if symptomatic or > 2 cm ^[4]	Benign, oestrogen-responsive. May regress post-menopause. Excise if large (to exclude phyllodes) or symptomatic.
Breast cyst	Reassurance. Aspiration. Surgery if recur or solid component present ^[4]	Aspiration is both diagnostic and therapeutic. Cytology only if: blood-stained aspirate, recur, radiologically suspicious ^[4]
Fibrocystic changes	Avoid caffeine. Evening primrose oil. Analgesics. COC ^[4]	Hormonal modulation to reduce oestrogen dominance. Caffeine may worsen breast pain (methyl-xanthine hypothesis).
Intraductal papilloma	Surgical excision (microdochectomy / major duct excision) ^[4]	Remove the affected duct to stop bloody discharge and rule out associated carcinoma.
Phyllodes tumour	Wide local excision with margin of at least 1 cm (mastectomy if adequate margin cannot be achieved) ^[4]	Margin of ≥ 1 cm required because phyllodes tumours have a leaf-like growth pattern with pseudopod-like extensions that can be missed with narrow margins. Can be malignant (metastasize via blood — ALND not required) ^[4]
Fat necrosis	Reassurance. Analgesics ^[4]. Should be biopsied to rule out carcinoma ^[5]	Self-limiting. But must biopsy because it mimics carcinoma clinically and radiologically.
Mastitis	Continue breastfeeding using the affected breast. Analgesics. Antibiotics (cloxacillin). Abscess: USG-guided aspiration or I&D (if necrotic skin) ^[4]	Continued breastfeeding prevents milk stasis → reduces bacterial growth medium. Cloxacillin covers S. aureus (most common cause).
Ductal ectasia	Conservative. Abscess: as above. Microdochectomy if persist ^[4]	Subareolar duct inflammation and fibrosis. Surgery only if persistent nipple discharge or abscess formation.
Mondor's disease	Reassurance. Analgesics (e.g. NSAID). Warm compression ^[4]	Self-limiting superficial sclerosing thrombophlebitis ^[4]. Resolves in weeks.

General indications for breast surgery for benign breast lumps ^[5]:

Patient choice: symptomatic, large size (cosmesis)
Discordance in triple assessment, e.g. clinico-radiological discordance

3. Skin Cancers

4. Breast Carcinoma — The Major Algorithm

This is the highest-yield management algorithm for localized lumps in clinical exams.

Approach to management of invasive breast cancer: multidisciplinary treatment (MDT) approach ^[5]^[25]:

Stage	Local Therapy	Regional Therapy	Systemic Therapy
Early stage (≤ T2N1)	BCT or mastectomy ± RT	SLNB (if cN0) or ALND (if cN1 or SLNB+) ± adjuvant RT	Adjuvant chemo/TT/hormonal for most patients
Locally advanced (T3 or N2+)	BCT or mastectomy ± RT (after neoadjuvant)	ALND ± adjuvant RT	Neoadjuvant chemo ± TT then adjuvant
Metastatic (stage IV)	Palliative local Tx	—	Palliative systemic Tx

^[25]

A. Local Therapy: Breast Surgery

Indications: C/I to BCS ^[27]

Type	Features	Indications	Contraindications
Simple mastectomy	Removal of breast tissue, preservation of axillary contents and pectoral muscles ^[26]	Clinically node –ve → SLNB should be performed ^[26]	—
Skin-sparing mastectomy	Preservation of overlying skin and inframammary fold → more natural shape ^[26]	Therapeutic mastectomy with immediate reconstruction (DCIS, Stage I–III). Prophylactic mastectomy ^[26]	Inflammatory breast cancer (cancer cell invasion of dermal lymphatics) ^[26]
Nipple-areolar sparing mastectomy	Preservation of dermis and epidermis of nipple but removal of major ducts ^[26]	Small-to-moderate breasts with minimal ptosis. Tumour < 2 cm with tumour-to-NAC distance > 2 cm. Prophylactic ^[26]	Inflammatory breast cancer. Paget's disease of nipple. Nipple changes or discharge ^[26]
Modified radical mastectomy (MRM)	Whole breast + overlying skin + axillary LN (level I + II) ^[27]	Clinically +ve LN	—

Drains: Jackson-Pratt drain (closed suction) ± 2nd drain at axilla if MRM → remove drains if output < 30 mL/day × 2 days ^[27]

Complications of mastectomy ^[27]^[25]:

Seroma, haematoma, wound infection
Skin flap / NAC necrosis (if reconstruction)
Arm morbidities: arm or shoulder pain, numbness, frozen shoulder
Phantom breast syndrome: altered chest wall sensation, might persist years after surgery
Post-mastectomy pain syndrome: up to 50%, often neuropathic ^[25]

B. Regional Therapy: Axillary Management

^[26]^[27]^[28]

SLNB: minimally invasive procedure designed to accurately stage cancers ^[23]

Indications ^[26]^[28]:

Early breast cancer with clinically –ve nodes (T1 or T2)
DCIS with planned mastectomy (because lymphatic drainage permanently altered after mastectomy → impossible to accurately perform SLNB later if invasive cancer found unexpectedly in mastectomy specimen) ^[26]
DCIS with suspicious features ( > 5 cm, palpable mass) ^[26]

Contraindications ^[26]:

Absolute: clinically +ve nodes (should be treated with ALND). Inflammatory breast cancer (T4d)
Relative: tumour size > 5 cm (T3). Tumour with chest wall or skin involvement (T4a–c). Previous breast or axillary procedures (disruption of lymphatic drainage → ↑ FN rate)

Technique ^[28]:

Dual tracer injection:
- Technetium-99m-labelled albumin: injected day before OT, C/I in pregnancy
- Methylene blue: injected intra-op for direct visualisation
Remove max 3–4 sentinel LN ^[28]
Injection should not be close to axilla (avoid interference), and lateral to previous scars (may block lymphatic drainage) ^[28]

Results ^[28]:

Finding	Action
No metastasis	NO NEED axillary dissection
Micrometastasis (≤ 2 mm)	NO NEED axillary dissection
Macrometastasis ( > 2 mm) × 1–2 LN	Controversial — if BCS + RT planned, completion ALND NOT required
Macrometastasis ( > 2 mm) × ≥ 3 LN	Axillary dissection
Extra-nodal extension	Axillary dissection
Sentinel LN not found	Axillary dissection

Therapy Type	Target	Agents	Indication
Chemotherapy	Rapidly dividing cells	Anthracyclines (doxorubicin), taxanes (paclitaxel/docetaxel), cyclophosphamide	Most invasive cancers; neoadjuvant for locally advanced; adjuvant for high-risk early stage
Hormonal therapy	ER/PR+ tumours	SERMs (tamoxifen), aromatase inhibitors (AI), ovarian ablation ^[25]	ER/PR+ tumours — tamoxifen for pre-menopausal, AI for post-menopausal
Targeted therapy	HER2+ tumours	Herceptin (trastuzumab), Tykerb (lapatinib), pertuzumab ^[25]	HER2+ tumours
Novel agents	Various	PARP inhibitor (BRCA-mutant), mTOR inhibitor, CDK4/6 inhibitor ^[25]	Specific molecular subtypes; metastatic disease

Neoadjuvant therapy ^[25]:

Indications: Locally advanced (T3+ or N2+) — difficult upfront resection + ↑↑ risk of recurrence. Selected early stage if wish to undergo BCT but ineligible (for downstaging)
Not suitable for those with extensive microcalcifications as these lesions (extensive DCIS) respond poorly to chemo
Preparation: should place radio-opaque clip at site of tumour (for subsequent resection)
Consists of: 6–8 cycles of chemotherapy ± HER2 inhibitor (trastuzumab + pertuzumab) for HER2+ patients
Post-neoadjuvant restaging by P/E ± imaging (often require MRI) if helpful in planning surgery
Pathological complete response (pCR): predicts good prognosis, occurs in 22% of patients

Bethesda	Cancer Risk	Management
I (Non-diagnostic)	1–4%	Repeat FNA or OT if radiologically suspicious
II (Benign)	0–3%	Clinical F/U
III (AUS/FLUS)	5–15%	Repeat FNA, molecular testing, hemiT if AUS × 2
IV (Follicular neoplasm)	15–30%	Hemithyroidectomy. Molecular testing
V (Suspicious)	60–75%	Hemithyroidectomy + frozen section + total thyroidectomy
VI (Malignant)	97–99%	Total thyroidectomy

^[15]^[16]

FNAC of thyroid: single most important Ix for thyroid nodule if TSH not depressed. Can proceed directly to total thyroidectomy if > 4 cm, gross invasion or LN +ve ^[15]

Frozen section is NOT helpful in hemithyroidectomy for follicular neoplasm — only gives diagnostic information in 13%, modifies surgical procedure in 3.3% with misguided intervention in 5%. One should wait for histology report after lobectomy ^[15]

Diagnosis	Management
Reactive lymphadenopathy	Treat the underlying cause (e.g., antibiotics for infection). Observe for resolution. If persistent ( > 4–6 weeks), biopsy.
TB lymphadenitis	Anti-TB therapy (RIPE regimen: rifampicin, isoniazid, pyrazinamide, ethambutol for 2 months then RI for 4 months). Rarely surgical.
Lymphoma	Excisional biopsy for diagnosis → then staging → chemotherapy ± RT (Hodgkin: ABVD; NHL: R-CHOP for DLBCL).
Metastatic carcinoma	Treat primary; FNAC/core biopsy for diagnosis; staging CT/PET; management depends on primary tumour.

Condition	Management	Rationale
Abscess	I&D (incision and drainage) ± antibiotics ± packing. USG-guided aspiration for deep or breast abscesses.	Antibiotics alone cannot penetrate a walled-off pus collection. You must break the wall and drain the pus.
Cellulitis	Antibiotics (flucloxacillin/cloxacillin for staph; penicillin for strep). Elevation of affected limb.	Treat the infection; no collection to drain.
Pilonidal sinus	Conservative: shave affected region, pluck sinus free of embedded hair, washout, antibiotics ^[8]. Acute: I&D. Chronic: removal of sinus tract + heal by secondary intention ^[8].	Remove hair and debris that perpetuate the foreign body reaction.

Tumour	Margin	Rationale
BCC (low risk)	4–6 mm ^[3]	Locally invasive but well-circumscribed; 95% cure with this margin
BCC (high risk / recurrent)	Mohs (100% margin assessment) ^[3]	Higher recurrence risk; tissue-sparing in cosmetically sensitive areas
SCC	5 mm (0.5 cm) ± LN dissection ^[6]	Can metastasize to LN → need wider margin and nodal assessment
Melanoma in-situ	5 mm	Confined to epidermis
Melanoma ≤ 1 mm	1 cm
Melanoma 1–2 mm	1–2 cm
Melanoma > 2 mm	2 cm
Phyllodes tumour	≥ 1 cm ^[4]	Pseudopod-like extensions; narrow margins → high recurrence
Breast carcinoma (BCS)	"No ink on tumour" ^[27]	With adjuvant RT, wider margin not needed for survival benefit
DCIS	≥ 2 mm ^[26]	Multifocal skip lesions; needs wider margin than invasive CA

High Yield Summary

Management of Localized Lumps — Key Exam Points:

Benign lumps: observe if asymptomatic and diagnosis is confident. Excise for symptoms, cosmesis, diagnostic uncertainty, or concern for malignancy.
Lipoma: excise if symptomatic, > 5 cm, or rapidly growing (r/o liposarcoma). Cx: scarring, seroma, haematoma ^[9]
Breast cancer management is an MDT approach: local (BCS + RT or mastectomy) + regional (SLNB or ALND) + systemic (chemo, hormonal, targeted).
BCT = BCS + compulsory adjuvant RT. C/I to BCS: multicentric disease, high tumour:breast ratio, persistent +ve margins, diffuse microcalcs, inflammatory CA. C/I to RT: prior RT, pregnancy, connective tissue disease (scleroderma) ^[27].
Breast margin: "no ink on tumour" for invasive CA ^[27]; ≥ 2 mm for DCIS ^[26]; ≥ 1 cm for phyllodes ^[4].
SLNB for clinically node-negative early breast cancer. C/I: clinically +ve nodes, inflammatory CA, T4.
ALND: Level I + II clearance. Level III NOT indicated unless grossly positive. 4 nerves at risk: long thoracic (winged scapula), thoracodorsal (lat dorsi weakness), intercostobrachial (paraesthesia medial arm), medial pectoral.
BCC: excision with 4–6 mm margin (low risk) or Mohs (high risk). SCC: excision with 5 mm margin ± LN dissection.
Melanoma: excision margin by Breslow thickness (in-situ = 5 mm, ≤ 1 mm = 1 cm, > 2 mm = 2 cm). SLNB if > 0.8 mm.
Thyroid: management per Bethesda — Bethesda IV (follicular neoplasm) → hemithyroidectomy; Bethesda VI (malignant) → total thyroidectomy.
Neoadjuvant therapy for breast cancer: locally advanced (T3+, N2+); place radio-opaque clip before chemo; consists of 6–8 cycles chemo ± anti-HER2.
Abscess = I&D. Antibiotics alone cannot penetrate walled-off pus.

Active Recall - Management of Localized Lumps

A. Complications of the Lump Itself (By Pathology)

1. Complications of Benign Lumps

Most benign lumps are innocuous — but they can still cause problems. The key concept is that even a benign lesion can become symptomatic or dangerous if it grows, gets infected, compresses vital structures, or undergoes (rare) malignant transformation.

2. Complications of Malignant Lumps

Complication	Mechanism	Examples
Local invasion	Tumour grows beyond capsule into adjacent structures	Thyroid CA → RLN palsy (hoarseness), tracheal compression (stridor), oesophageal invasion (dysphagia) ^[3]. Breast CA → fixation to chest wall. Skin cancer → bone/cartilage invasion
Ulceration	Tumour outgrows blood supply → central necrosis → skin breakdown	Fungating breast tumour; rodent ulcer (BCC); ulcerated SCC
Obstruction	Tumour compresses hollow viscus or duct	Thyroid → trachea; oesophageal CA → dysphagia; bile duct → jaundice
Haemorrhage	Erosion into blood vessel	Massive bleeding from aortic erosion by oesophageal CA; GI bleeding from ulcerated GI tumours
Fistula formation	Tumour erodes through wall of one structure into another	Tracheo-oesophageal fistula (→ aspiration pneumonia); colovesical fistula
Pathological fracture	Bone metastasis weakens bone → fracture with minimal trauma	Long bone fracture (femur most common); vertebral compression fracture

Complication	Mechanism
Lymph node metastasis	Tumour cells travel via lymphatics → regional LN involvement → hard, fixed, non-tender nodes
Lymphoedema	Lymphatic obstruction by tumour or post-surgical/radiation disruption of lymphatic drainage → oedema with high protein content ^[11]
Nerve involvement	Direct invasion or compression → neuropathy, paralysis

Site of Metastasis	Common Primary Tumours	Presentation
Bone	Breast, lung, prostate, thyroid, kidney	Bone pain, pathological fracture, hypercalcaemia (osteolytic lesions release calcium)
Lung/Pleura	Breast, colon, kidney	SOB, cough, pleural effusion
Liver	Colorectal, breast, lung	Hepatomegaly, jaundice, RUQ pain, deranged LFTs
Brain	Lung, breast, melanoma, RCC	Headache, seizures, focal neurological deficits
Adrenal	Lung, breast, melanoma	Usually asymptomatic; rarely adrenal insufficiency

B. Complications of Treatment

Timing	Complication	Pathophysiology
Immediate	Haemorrhage	Vessel injury during dissection
	Anaesthetic complications	Airway, cardiovascular, drug reactions
Early	Wound infection	Bacterial contamination (S. aureus most common)
	Haematoma	Ongoing ooze from wound bed → blood collects under skin flaps
	Seroma	Collection of serous fluid ^[26] — lymphatic disruption → serous fluid accumulates. Untreated seroma → delayed wound healing, wound infection, dehiscence, flap necrosis and poor cosmetic outcomes ^[26]
Late	Scarring / keloid / hypertrophic scar	Abnormal wound healing. Hypertrophic: confined to wound margin, regresses in 2–3 months. Keloid: extends beyond wound margins, continues to enlarge for 6 months to 1 year ^[30]
	Recurrence	Incomplete excision (especially sebaceous cyst, ganglion)
	Nerve injury	Inadvertent damage during dissection

This is a must-know topic for exams:

Complications of mastectomy ^[25]^[27]:

Seroma, haematoma, wound infection
Skin flap / NAC necrosis (if reconstruction) — ischaemia of skin flap edges → necrosis → may require debridement + skin graft ^[25]
Arm morbidities: arm or shoulder pain, numbness, frozen shoulder ^[27]
Phantom breast syndrome: altered chest wall sensation, might persist years after surgery ^[27]
Post-mastectomy pain syndrome: up to 50%, often associated with neuropathic phenomena (burning, aching, stiffness, paraesthesia) in axilla, upper arm, chest wall ^[25]

Complications of ALND — "4 nerves" plus other structures ^[28]^[25]:

Structure Injured	Result	Mechanism
Long thoracic nerve	Serratus anterior paralysis → pain, weakness, limitation of shoulder elevation, winging of scapula (↑ by pushing against wall) ^[25]	Runs on chest wall surface of serratus anterior → easily damaged if dissection goes too posteriorly
Thoracodorsal nerve (+ artery and vein)	Latissimus dorsi paralysis → unable to raise trunk with UL (e.g. climbing) ^[25], weak shoulder adduction and internal rotation ^[28]	Runs as a neurovascular bundle → should be identified and preserved
Intercostobrachial nerve	Paraesthesia of axilla, medial arm and lateral chest wall ^[28]. Easily damaged ^[25]	Sensory nerve that crosses the axilla — most commonly injured nerve during ALND
Medial pectoral nerve	Pec major weakness ^[28]	Runs deep to pec minor → at risk during Level II clearance
Axillary vein	Haemorrhage, upper limb oedema	Major vein in the axilla
Brachial plexus	Rare — motor and sensory deficit in upper limb	Far from axillary dissection → very rarely damaged except in extensive tumours ^[25]
Lymphatics	Upper limb lymphoedema (10–40%) ^[25] — ↑ risk if axillary RT	Disruption of axillary lymphatic drainage. Mx: arm physiotherapy, pneumatic compression devices, fitted compression sleeves ^[25]
	UL lymphangiosarcoma (Stewart-Treves syndrome) ^[28]	Rare late complication of chronic lymphoedema → malignant transformation of lymphatic endothelium. Typically presents 5–15 years post-mastectomy as purplish nodules on a chronically oedematous arm

Complications of breast implants ^[34]:

Complication	Description
Mechanical	Migration, malposition, exposure, rupture. Majority of rupture are often silent. Present with changes in breast shape/volume, capsular contracture, palpable lumps (breast or axilla), and pain
Implant infections	Managed by antibiotics ± explantation and irrigation of the pocket → closure over closed suction drainage
Capsular contracture	Esp. post-infection, radiation. Painful fibrous capsule around implant → palpable distortion of breast — Why? The body forms a fibrous capsule around any foreign body (normal response); excessive fibrosis contracts the capsule → compresses and distorts the implant
Breast implant associated anaplastic large cell lymphoma	ALK –ve, CD30 +ve. Disease confined to the capsule: capsulectomy alone is curative. Adjuvant therapies if needed: chemotherapy (cyclophosphamide, doxorubicin, vincristine, prednisone) or anti-CD30 (brentuximab vedotin)

^[34]

Stewart-Treves Syndrome — A Rare but High-Yield Complication

UL lymphangiosarcoma (Stewart-Treves syndrome) ^[28] is a rare but classic complication of chronic lymphoedema following mastectomy + ALND ± axillary RT. It presents years later as purplish-red nodules on a chronically swollen arm. The pathophysiology is thought to involve chronic lymphatic stasis → impaired immune surveillance → malignant transformation of lymphatic endothelial cells. It is highly aggressive with poor prognosis. This is a favourite exam viva question: "What is the late complication of chronic lymphoedema after breast cancer treatment?"

This is another must-know area. Complications of thyroidectomy ^[35]:

Timing	Complication	Pathophysiology and Clinical Features
Immediate (intraoperative)	Intraoperative bleeding	Thyroid is highly vascular; superior/inferior thyroid arteries
	Oesophageal injury	Posterior dissection
	Tracheal injury	Anterior dissection
	Tracheomalacia	Degeneration of tracheal cartilage following removal of compression by large goitre ^[35] → the trachea has been chronically compressed and the cartilage has become softened; once the goitre is removed, the trachea may collapse
	Thyroid storm	Develops in patients with longstanding untreated hyperthyroidism precipitated by surgery → rapid ↑ in serum thyroid hormone → ↑ response to catecholamines → hyperpyrexia, tachycardia, hypertension → heart failure with hypotension and arrhythmia ^[35]
	Superior laryngeal nerve (SLN) injury	SLN supplies the cricothyroid muscle which lengthens (tenses) the vocal cord to produce high-pitched sound → presents with vocal fatigue and changes in voice quality ^[35]. Important to ask if the patient is a professional singer pre-op ^[35]
	Recurrent laryngeal nerve (RLN) injury	RLN supplies all intrinsic muscles of larynx except cricothyroid ^[35]. Ipsilateral RLN injury → unilateral vocal cord palsy → hoarseness and ineffective cough ^[35]. Bilateral RLN injury → bilateral vocal cord palsy → stridor and dyspnoea (airway obstruction) ^[35]. ↑ risk of aspiration pneumonia ^[35]
Immediate ( < 24h)	Haematoma (1.25%)	Uncommon but fatal. Usually in paratracheal region below strap muscles → causes venous obstruction → acute laryngeal oedema → risk of airway compromise ^[35]. S/S: large, tense, firm immobile neck swelling + SOB ^[35]. Mx: cut subcuticular stitches and stitches holding strap muscles (evacuate all blood) → call seniors for intubation ^[35]
	Seroma	Superficial, mobile (self-limiting) ^[35]
Intermediate (1 day – 1 month)	Wound infection	Standard surgical wound infection
	Hypoparathyroidism → hypocalcaemia	MOST common complication ^[35]. Risk: 1–4% permanent (esp in cancer surgery), 10–20% transient (esp in ischaemia) ^[35]. Reason: often due to compromise of inferior thyroid artery ^[35] which supplies the parathyroid glands. S/S: CATS GO NUMB — Convulsion, Arrhythmia, Tetany, Laryngospasm, NUMBNESS (perioral, distal) ^[35]. Ix: serum Ca, ECG (long QT ± arrhythmia) ^[35]. Mx: Fast replacement — IV 10–20 mL of 10% calcium gluconate over 10 min (slow bolus). Replacement — calcium carbonate + calcitriol (vitamin D) ^[35]
	Hungry bone syndrome	May occur in those with pre-op hyperthyroidism → pre-op high bone turnover with sudden ↓ PTH → ↑↑↑ bone ossification → sudden hypocalcaemia ^[35]. The now-suppressed PTH can no longer mobilise calcium from bone, and the hyperactive osteoblasts (driven by previous high bone turnover) rapidly deposit calcium into bone
Late	Recurrence	Incomplete thyroidectomy for cancer
	Hypertrophic scar and keloid formation	Anterior neck is a high-tension wound
	Hypothyroidism	Expected after total thyroidectomy → requires lifelong levothyroxine replacement

Post-Thyroidectomy Haematoma — A Surgical Emergency!

Haematoma after thyroidectomy is uncommon (1.25%) but potentially fatal ^[35]. The paratracheal space is a closed compartment — even a small amount of blood causes venous congestion and laryngeal oedema → airway compromise can develop within minutes. The immediate management is to open the wound at the bedside (cut subcuticular stitches and strap muscle stitches) to evacuate blood ^[35]. Do NOT wait for the patient to go back to theatre — decompress at the bedside first, then intubate and return to OT for definitive haemostasis.

Lump	Complications of the Lump Itself	Complications of Treatment
Lipoma	Cosmesis, pain (if angiolipoma), functional impairment (internal), rare malignant transformation	Scarring, seroma, haematoma, recurrence (deep lipomas)
Sebaceous cyst	Infection (Cock's peculiar tumour), ulceration, sebaceous horn	Recurrence (if incomplete excision), scarring, infection
Ganglion	Nerve compression, pain	Recurrence (up to 50%), wound Cx, injury to neighbours
Haemangioma	Ulceration (MC), bleeding, airway Cx, visual Cx, high-output HF, Kasabach-Merritt	N/A (usually medical Mx — propranolol)
Breast carcinoma	Local invasion, skin changes, LN mets, distant mets (bone, lung, liver, brain)	Seroma, haematoma, nerve injuries (LTIM), lymphoedema, phantom breast, implant Cx
Thyroid lump	Compressive Sx (dyspnoea, dysphagia, dysphonia), thyrotoxicosis, thyroid storm	RLN injury, SLN injury, hypoparathyroidism/hypocalcaemia, haematoma, tracheomalacia, hungry bone syndrome
Skin cancer	Local invasion, LN mets (SCC, melanoma), distant mets (melanoma)	Scarring, wound infection, local recurrence, nerve injury (facial nerve in parotid area BCC)

High Yield Summary

Complications of Localized Lumps — Key Exam Points:

Sebaceous cyst complications: infection (most common — Cock's peculiar tumour mimics SCC), ulceration, sebaceous horn. Recurrence if incompletely excised — must remove entire cyst wall.
Haemangioma: ulceration is the most common complication. Beard distribution = risk of airway haemangioma. Upper medial eyelid = astigmatism, amblyopia, proptosis. Kasabach-Merritt syndrome = consumptive coagulopathy in giant haemangioma.
ALND complications (4 nerves): Long thoracic (winged scapula), Thoracodorsal (lat dorsi weakness), Intercostobrachial (paraesthesia medial arm — most commonly injured), Medial pectoral (pec major weakness). Plus lymphoedema (10–40%), and late Stewart-Treves syndrome (lymphangiosarcoma).
Post-thyroidectomy hypocalcaemia: most common complication — due to damage/devascularisation of parathyroid glands. CATS GO NUMB: Convulsion, Arrhythmia, Tetany, Laryngospasm, Numbness. Mx: IV calcium gluconate then oral calcium + calcitriol.
Post-thyroidectomy haematoma: uncommon but potentially fatal — open wound at bedside immediately (cut stitches to evacuate blood).
RLN injury: unilateral = hoarseness + ineffective cough; bilateral = stridor + dyspnoea (airway emergency). SLN injury = vocal fatigue, cannot sing high pitch.
Breast implant complications: capsular contracture (most common late Cx), rupture (often silent), infection, breast implant-associated anaplastic large cell lymphoma (BIA-ALCL).
Percutaneous biopsy Cx: bleeding, infection, organ injury, pneumothorax (lung Bx: 10–30%), needle tract tumour seeding (rare).
Post-mastectomy pain syndrome: up to 50%, neuropathic in character — an important and under-recognised complication.

Active Recall - Complications of Localized Lumps

^[1] Senior notes: felixlai.md (Lipoma section — sarcomatous change risk factors) ^[3] Senior notes: Ryan Ho Endocrine.pdf (p18 — Thyroid lump complications: pain, compressive, thyroid storm) ^[7] Senior notes: Ryan Ho Rheumatology.pdf (p168 — Dermoid cyst CNS connection) ^[9] Senior notes: Ryan Ho Rheumatology.pdf (p169 — Lipoma prognosis, treatment complications, painful lipoma causes) ^[10] Senior notes: maxim.md (Ganglion cyst — nerve impingement, recurrence) ^[11] Senior notes: maxim.md (Section 4.6 Lymphoedema) ^[12] Senior notes: Ryan Ho Rheumatology.pdf (p178 — Pyogenic granuloma bleeding risk, management) ^[21] Senior notes: Ryan Ho GI.pdf (p259 — Hepatic haemangioma: FNAC contraindicated, Kasabach-Merritt syndrome) ^[25] Senior notes: Ryan Ho Urogenital.pdf (pp208, 210 — Mastectomy complications, ALND complications, post-mastectomy pain syndrome, lymphoedema management) ^[26] Senior notes: felixlai.md (Mastectomy complications — seroma; SLNB and ALND complications) ^[27] Senior notes: maxim.md (Mastectomy complications — seroma, haematoma, wound infection, skin flap necrosis, phantom breast syndrome) ^[28] Senior notes: maxim.md (ALND complications — 4 nerves, lymphoedema, Stewart-Treves syndrome) ^[30] Senior notes: Ryan Ho Fundamentals.pdf (pp164, 167, 168 — Dermoid cyst complications, sebaceous cyst complications, pyogenic granuloma complications, Baker's cyst complications, keloid/hypertrophic scar) ^[31] Senior notes: Ryan Ho Rheumatology.pdf (p164 — Sebaceous cyst complications: infection, Cock's peculiar tumour, ulceration, sebaceous horn) ^[32] Senior notes: felixlai.md (Haemangioma complications — ulceration, bleeding, airway, periorbital) ^[33] Senior notes: Ryan Ho Rheumatology.pdf (p176 — Haemangioma complications: ulceration, airway, periorbital) ^[34] Senior notes: maxim.md (Complications of breast implants — mechanical, infection, capsular contracture, BIA-ALCL) ^[35] Senior notes: felixlai.md (Complications of thyroidectomy — complete table); Senior notes: Ryan Ho Endocrine.pdf (p22 — Thyroidectomy complications) ^[36] Senior notes: Ryan Ho Diagnostic Radiology.pdf (p80 — Percutaneous biopsy complications)

High Yield Summary

Key Points for Exam:

Systematic approach to any lump: History → Inspection → Palpation → Special tests → Regional LN → Systemic
Lipoma = most common benign soft tissue neoplasm — soft, mobile, slip sign positive, subcutaneous, not attached to skin
BCC = most common skin cancer in Chinese — face (medial canthus), pigmented in Asians, rodent ulcer, locally invasive but almost never metastasizes
Fibroadenoma = most common benign breast tumour — rubbery, highly mobile "breast mouse", reproductive age
Benign vs malignant features: Benign = well-defined, smooth, soft/rubbery, mobile, slow-growing. Malignant = hard, irregular, fixed, non-tender, rapid growth, skin changes, LN involvement
Red flags: rapid growth, > 5 cm, deep to fascia, hard/irregular, fixed, skin changes (dimpling, peau d'orange, ulceration), LN, constitutional symptoms
Breast triple assessment: clinical + radiological + pathological — must know for exam
Breast risk factors: ↑ oestrogen (early menarche, late menopause, nulliparity, no breastfeeding, COC/HRT), FHx (BRCA), previous breast pathology, radiation, lifestyle
Thyroid lump red flags for malignancy: male, age < 14 or > 70, solitary nodule, firm/hard, fixed, pressure symptoms/RLN palsy, cervical LN, neck irradiation, FHx thyroid CA
Layer determines differential: always think which tissue layer the lump arises from based on mobility testing
For neck lumps, DDx includes: thyroid enlargement, lymphadenopathy, skin lumps, branchial cyst, thyroglossal duct cyst
Fat necrosis can mimic breast carcinoma clinically AND radiologically — always ask about trauma history or breast procedures

High Yield Summary

Differential Diagnosis of Localized Lump — Key Exam Points:

Use the layer-based approach: the examination findings (mobility, skin attachment, buttonhole sign, slip sign, punctum) tell you which layer → which differential
Anterior neck lump DDx: thyroid enlargement, lymphadenopathy, skin lumps, branchial cyst, thyroglossal duct cyst ^[3]
Groin lump DDx: inguinal/femoral hernia, femoral artery aneurysm, saphenous varix, inguinal LN, lymphoma, lipoma, abscess, undescended testis, hydroceles ^[1]
Breast lump DDx: fibroadenoma (mobile, rubbery), cyst (fluctuant), fibrocystic changes (cyclical), fat necrosis (mimics CA), carcinoma (hard, fixed), intraductal papilloma (bloody discharge), phyllodes (> 40y, can be malignant)
BCC vs SCC vs keratoacanthoma: BCC = rolled edge, rodent ulcer, pigmented in Asians, rarely metastasises. SCC = everted edge, contact bleeding, ± LN. KA = volcano-like, central keratin crater, rapid growth then regression — but always excise to r/o SCC ^[6]
Fat necrosis and sclerosing adenosis mimic breast carcinoma clinically AND radiologically → must biopsy ^[4]
FNAC is useless for lymphoma — need excisional biopsy for architectural detail ^[11]
Lymph node consistency: Hard = solid malignancy. Firm/rubbery = lymphoma, chronic leukaemia. Soft = acute leukaemia, reactive ^[11]
Dermoid cyst DDx: sebaceous cyst (punctum), lipoma (softer, mobile), and site-dependent (pilonidal, thyroglossal, craniopharyngioma) ^[7]
Ganglion: most common soft tissue tumour of hands, dorsal wrist 70%, transilluminant, never becomes malignant ^[10]

High Yield Summary

Diagnostic Criteria and Investigation — Key Exam Points:

Triple assessment (clinical + radiological + histopathological) is the gold standard for breast lump workup — overall Sens 99.6%, Spec 93% — positive when ANY one is positive ^[13]^[14]
BI-RADS classification: 0 = more imaging, 1 = negative, 2 = benign, 3 = probably benign (F/U 6 mo), 4 = suspicious (Bx), 5 = highly suspicious (Bx), 6 = proven malignancy
Mammography: most sensitive breast imaging; use > 35–40y; insensitive in young/Asian dense breasts; spiculated mass (~90% malignant); linear branching microcalcifications suggest DCIS
Breast USG: first-line for < 35y/pregnant; taller-than-wide = suspicious; central vascularity = suspicious
MRI breast: highest sensitivity (88–100%) but low specificity; used for BRCA screening, lobular CA, occult primary, neoadjuvant monitoring
Core biopsy preferred over FNAC when suspecting malignancy — FNAC cannot distinguish DCIS from invasive CA, cannot do reliable IHC
Thyroid: TFT + USG for all → FNA of suspicious nodules (TI-RADS) → Bethesda classification → low TSH: scintigraphy first (hot = no FNA, cold = FNA)
Bethesda system: I = non-diagnostic (repeat), II = benign, III = AUS (repeat), IV = follicular neoplasm (lobectomy), V = suspicious (lobectomy ± total), VI = malignant (total thyroidectomy)
Pigmented lesions: ABCDE system + dermoscopy + excision biopsy; Evolution (E) is the most important criterion
FNAC is contraindicated in hepatic haemangioma (haemorrhage risk) and useless for lymphoma (no architecture)
Soft tissue mass red flags ( > 5 cm, deep to fascia, rapid growth) → urgent MRI + core biopsy → refer sarcoma MDT

High Yield Summary

Management of Localized Lumps — Key Exam Points:

Benign lumps: observe if asymptomatic and diagnosis is confident. Excise for symptoms, cosmesis, diagnostic uncertainty, or concern for malignancy.
Lipoma: excise if symptomatic, > 5 cm, or rapidly growing (r/o liposarcoma). Cx: scarring, seroma, haematoma ^[9]
Breast cancer management is an MDT approach: local (BCS + RT or mastectomy) + regional (SLNB or ALND) + systemic (chemo, hormonal, targeted).
BCT = BCS + compulsory adjuvant RT. C/I to BCS: multicentric disease, high tumour:breast ratio, persistent +ve margins, diffuse microcalcs, inflammatory CA. C/I to RT: prior RT, pregnancy, connective tissue disease (scleroderma) ^[27].
Breast margin: "no ink on tumour" for invasive CA ^[27]; ≥ 2 mm for DCIS ^[26]; ≥ 1 cm for phyllodes ^[4].
SLNB for clinically node-negative early breast cancer. C/I: clinically +ve nodes, inflammatory CA, T4.
ALND: Level I + II clearance. Level III NOT indicated unless grossly positive. 4 nerves at risk: long thoracic (winged scapula), thoracodorsal (lat dorsi weakness), intercostobrachial (paraesthesia medial arm), medial pectoral.
BCC: excision with 4–6 mm margin (low risk) or Mohs (high risk). SCC: excision with 5 mm margin ± LN dissection.
Melanoma: excision margin by Breslow thickness (in-situ = 5 mm, ≤ 1 mm = 1 cm, > 2 mm = 2 cm). SLNB if > 0.8 mm.
Thyroid: management per Bethesda — Bethesda IV (follicular neoplasm) → hemithyroidectomy; Bethesda VI (malignant) → total thyroidectomy.
Neoadjuvant therapy for breast cancer: locally advanced (T3+, N2+); place radio-opaque clip before chemo; consists of 6–8 cycles chemo ± anti-HER2.
Abscess = I&D. Antibiotics alone cannot penetrate walled-off pus.

High Yield Summary

Complications of Localized Lumps — Key Exam Points:

Sebaceous cyst complications: infection (most common — Cock's peculiar tumour mimics SCC), ulceration, sebaceous horn. Recurrence if incompletely excised — must remove entire cyst wall.
Haemangioma: ulceration is the most common complication. Beard distribution = risk of airway haemangioma. Upper medial eyelid = astigmatism, amblyopia, proptosis. Kasabach-Merritt syndrome = consumptive coagulopathy in giant haemangioma.
ALND complications (4 nerves): Long thoracic (winged scapula), Thoracodorsal (lat dorsi weakness), Intercostobrachial (paraesthesia medial arm — most commonly injured), Medial pectoral (pec major weakness). Plus lymphoedema (10–40%), and late Stewart-Treves syndrome (lymphangiosarcoma).
Post-thyroidectomy hypocalcaemia: most common complication — due to damage/devascularisation of parathyroid glands. CATS GO NUMB: Convulsion, Arrhythmia, Tetany, Laryngospasm, Numbness. Mx: IV calcium gluconate then oral calcium + calcitriol.
Post-thyroidectomy haematoma: uncommon but potentially fatal — open wound at bedside immediately (cut stitches to evacuate blood).
RLN injury: unilateral = hoarseness + ineffective cough; bilateral = stridor + dyspnoea (airway emergency). SLN injury = vocal fatigue, cannot sing high pitch.
Breast implant complications: capsular contracture (most common late Cx), rupture (often silent), infection, breast implant-associated anaplastic large cell lymphoma (BIA-ALCL).
Percutaneous biopsy Cx: bleeding, infection, organ injury, pneumothorax (lung Bx: 10–30%), needle tract tumour seeding (rare).
Post-mastectomy pain syndrome: up to 50%, neuropathic in character — an important and under-recognised complication.

Localized Lump

Definition and Key Concepts

Epidemiology and Risk Factors

General Epidemiological Points

Risk Factors for Malignant Lumps (General Principles)

Anatomy and Function Relevant to Localized Lumps

Layers (Superficial to Deep)

Site-Specific Anatomy

Etiology

Relevant Classification Systems

A. Classification by Nature (Surgical Sieve)

B. Classification by Layer/Depth

C. Classification by Site

D. Benign vs. Malignant Features

Clinical Features

A. History (Symptoms)

1. Characteristics of the Lump Itself

2. Associated / Systemic Symptoms

3. Risk Factor Enquiry (Site-Dependent)

B. Physical Examination (Signs)

1. Inspection

2. Palpation

3. Special Tests by Site

4. Regional Examination

5. Systemic Examination

Summary of Clinical Approach to a Localized Lump

Active Recall - Localized Lump

References

Overarching Framework: The Layer-Based Differential

Site-Specific Differentials

A. Differential Diagnosis of an Anterior Neck Lump

B. Differential Diagnosis of a Groin Lump

C. Differential Diagnosis of a Breast Lump

D. Differential Diagnosis of a Skin Lump/Ulcer

BCC vs SCC vs Keratoacanthoma vs Melanoma

Epidermoid Cyst vs Lipoma vs Dermoid Cyst vs Dermatofibroma

E. Differential Diagnosis of a Subcutaneous Cystic/Soft Lump

F. Differential Diagnosis of Lymphadenopathy Presenting as a Lump

G. Differential Diagnosis of Vascular Lumps

Diagnostic Decision-Making Flowchart

Special Differentials Worth Remembering

Approach Summary: The "5-Question" DDx Framework

Active Recall - Differential Diagnosis of Localized Lump

Diagnostic Criteria, Diagnostic Algorithm, and Investigation Modalities for Localized Lumps

Standardised Reporting and Classification Systems

1. BI-RADS (Breast Imaging Reporting And Data System)

2. TI-RADS (Thyroid Imaging Reporting And Data System)

3. Bethesda System for Reporting Thyroid Cytopathology

4. ABCDE Criteria for Pigmented Lesions (Melanoma Screening)

The Triple Assessment (Gold Standard for Breast Lumps)

Investigation Modalities: Detailed Breakdown

A. Imaging

i. Ultrasound (USG)

ii. Mammography

iii. MRI

iv. CT Scan

v. Thyroid Scintigraphy (Nuclear Medicine)

vi. Sentinel Lymph Node Identification (Nuclear Medicine)

vii. Dermoscopy

B. Tissue Diagnosis (Biopsy)

i. Fine Needle Aspiration Cytology (FNAC)

ii. Core Needle Biopsy (CNB)

iii. Excisional / Incisional Biopsy

iv. Skin Punch Biopsy

C. Blood Tests

D. Other Investigations

Master Diagnostic Algorithm

Site-Specific Investigation Summaries

Breast Lump Investigation Algorithm

Thyroid Nodule Investigation Algorithm

Skin Lump Investigation Algorithm

Active Recall - Diagnostic Criteria and Investigations for Localized Lump

References

Management of Localized Lumps

General Principles of Management

A. Observation (Conservative / Watchful Waiting)

B. Excision (Surgical Removal)

C. Multimodal Treatment (Surgery + Adjuvant Therapies)

Management by Pathology Type

1. Benign Soft Tissue Lumps