Benign Breast Disease

• The breast overlies the pectoralis major muscle from the 2nd to 6th rib vertically and from the sternal edge to the mid-axillary line horizontally.
• The axillary tail of Spence extends into the axilla — a common site for accessory breast tissue and palpable masses.
• The breast is divided into four quadrants (upper outer, upper inner, lower outer, lower inner) plus the central/subareolar region. The upper outer quadrant contains the most glandular tissue (~50%), which is why most pathology (benign and malignant) occurs here.

The functional unit of the breast is the TDLU, consisting of:

• Terminal duct (the smallest duct segment)
• Lobule (a cluster of acini/ductules that produce milk)
• Intralobular stroma (hormonally responsive connective tissue surrounding lobules)
• Extralobular stroma (fibrous and adipose tissue)

Why does this matter? Because the vast majority of both benign and malignant breast pathology arises from the TDLU. Cysts arise from distension of the TDLU. Fibroadenomas arise from the stroma and epithelium of the TDLU. Ductal carcinoma arises from the ductal epithelium of the TDLU.

• 15–20 lactiferous ducts converge on the nipple, each draining a lobe.
• Beneath the areola, ducts widen into lactiferous sinuses before opening at the nipple.
• Intraductal papillomas arise within these ducts (especially the large subareolar ducts for solitary papillomas).

• ~75% drains to axillary lymph nodes (Levels I, II, III relative to pectoralis minor).
• Remaining drains to internal mammary nodes, supraclavicular nodes, and contralateral breast.
• Benign reactive lymphadenopathy can occur with inflammatory breast conditions and even large phyllodes tumours.

• Breast tissue expresses oestrogen receptors (ER) and progesterone receptors (PR).
• During the menstrual cycle:
  • Follicular phase → oestrogen stimulates ductal proliferation
  • Luteal phase → progesterone stimulates lobular differentiation and fluid retention → explains cyclical breast pain and nodularity
  • Menstruation → hormone withdrawal → apoptosis and involution
• This cyclical proliferation-and-involution underpins fibrocystic changes and is why symptoms worsen premenstrually.

This is the most clinically important classification because it directly informs surveillance strategy.

A practical clinical grouping:

1. Fibrocystic breast changes (the spectrum of non-proliferative → proliferative ± atypia)
2. Benign neoplasms (fibroadenoma, intraductal papilloma, phyllodes tumour, adenoma)
3. Infective and inflammatory conditions (lactational mastitis/abscess, periductal mastitis, duct ectasia, fat necrosis, Mondor's disease, idiopathic granulomatous mastitis)
4. Proliferative stromal lesions (diabetic mastopathy, pseudoangiomatous stromal hyperplasia)
5. Gynaecomastia (benign breast disease of males)

Etiology:

• Unknown, but believed to result from hormonal imbalance — oestrogen predominance over progesterone ^[3].
• During each menstrual cycle, oestrogen drives ductal epithelial proliferation and stromal oedema; progesterone modulates this. When the ratio is skewed (relative oestrogen excess), the proliferative stimulus is excessive and the cyclical involution is incomplete.
• Over many cycles, this results in a spectrum of histological changes: stromal fibrosis, macro- and microcysts, apocrine metaplasia, epithelial hyperplasia, and adenosis.

Pathophysiology of specific components:

• Arise from the TDLU due to distension and obstruction of the efferent ductule ^[3].
• As lobules involute (typically after age 35), the ductule may become blocked → fluid secreted by the epithelium accumulates → cyst formation.
• Cysts can enlarge rapidly (causing sudden-onset pain) or remain stable.
• Cyst fluid is typically straw-coloured or green-brown. Blood-stained fluid is concerning and requires cytological analysis to exclude intracystic carcinoma or papilloma.

ADH:

• Proliferation of uniform epithelial cells with monomorphic round nuclei filling part but not all of the involved duct ^[3].
• Architecturally and cytologically resembles low-grade DCIS, but does not completely fill the duct cross-section (if it did, it would be classified as DCIS).
• Confers 4–5× increased risk of subsequent invasive carcinoma in both the ipsilateral and contralateral breast — indicating it is a risk marker for the whole breast, not just a local precursor.

ALH:

• Monomorphic, evenly spaced, dyshesive cells filling part but not all of the involved lobule ^[3].
• "Dyshesive" = cells lose intercellular adhesion (due to loss of E-cadherin, the same molecular hallmark as lobular carcinoma) — this is why ALH is considered on a spectrum with LCIS.

• Most common benign tumour of the breast ^[3][4].
• A fibroepithelial neoplasm — contains both glandular (epithelial) and stromal (fibrous) components, both arising from the TDLU.
• Likely hormonal-dependent ^[3]:
  • Increases in size during pregnancy or with oestrogen-based OC pills
  • Persists during reproductive years
  • Regresses or decreases after menopause
• Simple fibroadenoma → NO increased risk of breast cancer ^[3].
• Complex fibroadenoma (contains proliferative changes like papillary apocrine changes, ductal hyperplasia, sclerosing adenosis) → slightly higher risk of subsequent cancer ^[3].
• Giant fibroadenoma (> 10 cm) should be excised because it cannot be distinguished from Phyllodes tumour on physical examination or imaging ^[3].
• Juvenile fibroadenoma (age 10–18) should be followed up carefully; excision is recommended if > 5 cm or persists to adulthood ^[3].

• Phyllodes comes from Greek "phyllon" = leaf — describes the characteristic leaf-like papillary projections on histology ^[3].
• A fibroepithelial tumour that resembles fibroadenoma both clinically and on imaging, but has a hypercellular stroma with stromal overgrowth.
• Classified as benign (60–75%), borderline (15–20%), or malignant (10–25%) based on stromal cellularity, mitotic rate, stromal atypia, margins, and stromal overgrowth ^[3][4].
  • Benign → propensity to recur locally if excision margins are inadequate.
  • Malignant → can metastasize distantly, commonly to the lungs via haematogenous spread. The stroma degenerates into sarcomatous tissue lacking an epithelial component ^[3]. This is why axillary lymph node dissection (ALND) is NOT required — spread is haematogenous, not lymphatic ^[4].
• Associated with Li-Fraumeni syndrome (AD, TP53 germline mutation) ^[3].

• A benign tumour of the epithelium of the mammary ducts, consisting of a fibrovascular core covered by epithelial and myoepithelial cells ^[3].
• Solitary papilloma typically arises in a large subareolar duct → classic presentation is bloody nipple discharge (because the fibrovascular core is friable and bleeds easily).
• Multiple papillomas (diffuse papillomatosis, defined as ≥ 5 papillomas in a localized segment) arise more peripherally and carry a higher risk of associated carcinoma ^[4].
• Associated with a slightly increased risk of developing breast cancer (proliferative lesion without atypia = 1.5–2×) ^[3].

• "Ectasia" from Greek "ektasis" = dilation.
• Characterised by dilatation of subareolar ducts with periductal fibrosis and inflammation ^[3].
• An age-related involutionary phenomenon — typically occurs in older women (perimenopausal/postmenopausal).
• The dilated ducts accumulate inspissated secretions → cheesy, creamy discharge.
• Periductal fibrosis can cause nipple retraction (by shortening/tethering the duct).
• Blockage of ducts predisposes to periductal mastitis or breast abscess ^[3].
• NOT associated with increased risk of breast cancer ^[3].
• Not associated with significant periareolar inflammation or infection (distinguishes it from periductal mastitis) ^[3].
• Smoking is a risk factor (toxic metabolites in tobacco damage the subareolar ducts and predispose to periductal inflammation) ^[2].

• Most common in the first 3 months of breastfeeding ^[2][3].
• Pathogenesis: During breastfeeding, nipple trauma (cracks/fissures) allows skin commensals to enter → organisms grow in stagnant milk (breast milk naturally contains bacteria) → ascending infection → mastitis.
• Most common organism: Staphylococcus aureus ^[2].
• Progresses to abscess formation in ~25% of patients ^[3].
  • Abscess is often NOT fluctuant in the early/late stages (because it sits deep within the breast parenchyma surrounded by oedematous tissue) — this is a common exam pitfall.
  • Diagnosis of abscess is made by failure to respond to antibiotics, USG evidence of abscess cavity, or aspiration of pus ^[3].

• Occurs in younger women (unlike duct ectasia), strongly associated with smoking ^[3].
• Pathogenesis: Smoking → toxic metabolites damage the subareolar duct epithelium → squamous metaplasia of the duct lining → obstruction → duct dilation → secondary bacterial infection (often mixed anaerobic organisms including Bacteroides, or S. aureus) → periductal inflammation → may form subareolar abscess.
• If the abscess drains (spontaneously or surgically) but the underlying diseased duct is not excised → recurrence → formation of a mammary duct fistula (communication between the subareolar duct and the skin, usually at the areolar margin) ^[3].
• Recurrence is the rule unless the fistula is laid open and the diseased duct excised ± total duct excision.

• Ischaemic necrosis of fat lobules ^[2].
• Risk factors: Trauma (seatbelt injury, sports injury), iatrogenic (especially after breast reconstruction, reduction mammoplasty, radiotherapy) ^[2].
• Pathophysiology: Damaged adipocytes release lipid → inflammatory response → foreign body giant cell reaction → fibrosis and calcification.
• Mimics carcinoma both clinically and radiologically — can present as a painless hard lump with skin dimpling, nipple retraction, and spiculated mass with calcification on mammogram ^[2]. Core biopsy is required to differentiate from cancer.

• Superficial sclerosing thrombophlebitis of the breast and anterior chest wall ^[2].
• "Mondor" = named after Henri Mondor, French surgeon.
• Pathophysiology: Thrombosis of superficial veins (most commonly the thoraco-epigastric vein, also lateral thoracic vein, superior epigastric vein) → inflammation → sclerosis → palpable subcutaneous cord.
• Often idiopathic; can follow trauma, surgery, or excessive physical activity.
• Self-limiting — resolves with conservative management (NSAIDs, warm compression) ^[2].

• A rare benign inflammatory breast disease of unknown etiology that mimics breast cancer clinically and radiologically ^[3].
• Occurs in young parous women within a few years of pregnancy (but can occur in nulliparous women).
• Association with Corynebacterium kroppenstedtii infection ^[3].
• Self-limiting — resolves slowly with complete resolution in 9–12 months ^[3].
• NO increased risk of subsequent breast cancer ^[3].
• Diagnosis of exclusion after excluding TB, sarcoidosis, histoplasmosis, GPA (Wegener's) ^[3].
• Histology: granulomatous lesions centred on breast lobules — non-caseating granulomas (unlike TB which is caseating).

Diabetic (DM) Mastopathy:

• Also known as lymphocytic mastitis/lymphocytic mastopathy ^[3].
• Occurs in premenopausal women with Type 1 DM.
• Unknown etiology — may represent an autoimmune reaction (associated with longstanding insulin-dependent diabetes, often with other autoimmune complications like retinopathy/nephropathy).
• Presents as a hard, irregular, painless mass that can mimic carcinoma.
• Does NOT increase risk of subsequent breast cancer ^[3].

Pseudoangiomatous Stromal Hyperplasia (PASH):

• A benign stromal proliferation that simulates a vascular lesion on histology (the slit-like spaces lined by myofibroblasts can look like blood vessels, hence "pseudoangiomatous") ^[3].
• Presents as a mass or thickening.
• Does NOT increase risk of subsequent breast cancer ^[3].

• "Gynaecomastia" from Greek: "gyne" = woman, "mastos" = breast — literally "woman's breast."
• Benign enlargement of the male breast resulting from glandular proliferation ^[4].
• Distinguish from pseudo-gynaecomastia (lipomastia) = fat deposition without glandular proliferation (the "man boob" of obesity).

Etiology — change in oestrogen:androgen activity ratio ^[4]:

Symptoms:

Signs:

Symptoms:

Signs:

Symptoms:

Signs (the classic "breast mouse"):

Why is it called a "breast mouse"? Because it is so mobile that it seems to dart away from your examining fingers, like a mouse escaping.

Symptoms:

Signs:

Symptoms:

Signs:

Symptoms:

Signs:

Symptoms:

Signs:

Symptoms:

Signs:

Symptoms & Signs — Mimics carcinoma clinically ^[2]:

Symptoms & Signs:

Symptoms & Signs — Mimics breast cancer ^[3]:

Symptoms & Signs ^[4]:

Suspect malignancy if ^[4]:

• Old patient without risk factors
• Unilateral gynaecomastia
• Non-tender hard mass within breast tissue
• Lymphadenopathy

• Cyclical: Fibrocystic changes (most common) — bilateral, diffuse, premenstrual
• Non-cyclical: Acute mastitis, fibroadenoma, inflammatory breast cancer
• Management approach:
  • Cyclical or bilateral diffuse pain: No imaging required, reassurance, conservative (NSAIDs)
  • Non-cyclical / unilateral / focal pain: USG/mammogram to investigate

Key history questions:

• True nipple discharge? (vs. fluid from skin lesion)
• Unilateral or bilateral?
• Colour?
• Recent pregnancy/breastfeeding?

Pathological nipple discharge (concerning features): unilateral, single-duct, bloody, spontaneous

Investigations: Triple assessment ± nipple discharge cytology ± ductogram/ductoscopy ^[2].

Let's now walk through each differential systematically, explaining why each condition presents the way it does and how to distinguish them:

• Who: Young women 15–35 (peak reproductive age) ^[3][4]
• Why this age? Fibroadenoma is a hormonally-dependent fibroepithelial neoplasm — it develops during the period of maximal lobular development and oestrogen stimulation.
• Key distinguishing features: Well-defined, rubbery, highly mobile, non-tender ^[3]. The high mobility ("breast mouse") occurs because it is encapsulated with no desmoplastic reaction tethering it to surrounding tissue.
• What could fool you? A small phyllodes tumour is clinically indistinguishable from fibroadenoma — suspect phyllodes if the mass is large ( > 5 cm), rapidly growing, or in an older patient ( > 40) ^[3].
• Cancer risk: Simple fibroadenoma = NO increased risk. Complex fibroadenoma = slightly increased risk ^[3].

• Who: Perimenopausal women (35–55), during the involution phase of the ANDI framework ^[2][4]
• Why this age? As lobules involute, efferent ductules may become obstructed → fluid accumulates → cyst formation. This is a normal part of breast involution gone slightly awry.
• Key distinguishing features: Soft to firm (depending on tension), fluctuant, smooth, mobile, may be tender (especially if enlarging rapidly) ^[3].
• What could fool you? A tense cyst can feel firm and mimic a solid mass. USG easily resolves this — cysts are anechoic with posterior acoustic enhancement. Also, an intracystic papilloma or intracystic carcinoma can have a solid component within the cyst wall — blood-stained aspirate or a solid component on USG mandates further investigation ^[2][4].

• Who: Reproductive-age women (25–55) ^[3][4]
• Why? Exaggeration of normal cyclical hormonal changes → stromal fibrosis + microcysts + hyperplasia.
• Key distinguishing features: Cyclical painful nodularity (not a discrete mass), bilateral, upper outer quadrants, worsens premenstrually. Serosanguinous nipple discharge may occur ^[4].
• What could fool you? A dominant area of fibrosis can feel like a discrete mass and mimic carcinoma. If there's a dominant palpable abnormality, it must undergo triple assessment.

• Who: Older women ( > 40, median 42–45) ^[3]
• Why important? Straddles the benign-malignant spectrum. Can be malignant and metastasize via blood (not lymph) — ALND not required ^[4].
• Key distinguishing features: Smooth, painless, mobile mass — resembles a large fibroadenoma but with rapid growth and often large size. Overlying skin may be shiny and stretched ^[3].
• Red flags for malignancy: Very large size, rapid growth, cystic areas on USG.

• Who: Any age, but key history of trauma or iatrogenic cause (e.g., breast reconstruction) ^[2]
• Why it mimics cancer: Ischaemic necrosis of fat lobules → inflammatory response → fibrosis and dystrophic calcification → hard, irregular, fixed mass with skin dimpling, nipple retraction. Mimics CA both clinically AND radiologically ^[2][4]. Core biopsy is required to differentiate ^[2].
• Key distinguishing feature from cancer: History of trauma/surgery + ecchymosis. But even with this history, biopsy is mandatory.

• Who: Any age
• Why? Benign adipose tissue tumour; can occur in the subcutaneous tissue overlying the breast.
• Key distinguishing features: Soft, well-defined, lobulated, non-tender, mobile. Sits in the subcutaneous plane (movable with the skin, not deep to it).
• What could fool you? Large lipomas can be hard to distinguish from other soft masses by palpation alone. USG shows a well-circumscribed, compressible, echogenic mass.

• Who: Older women ( > 35, rising steeply after 50); median age 55 in Hong Kong ^[5]
• Key distinguishing features: Hard, irregular, fixed, non-tender mass, mostly at the upper outer quadrant ^[5]. Skin tethering, peau d'orange, nipple retraction, bloody nipple discharge, axillary lymphadenopathy.
• Special types that can present differently:
  • Paget's disease of the nipple: Eczematous changes involving the nipple → associated with malignancy within the same breast → malignant epithelial (Paget) cells infiltrate and proliferate in the epidermis, causing thickening of the nipple and areolar skin ^[1][8][9]. 97% has underlying breast carcinoma, about half present with a breast mass ^[9]. 50–60 years old ^[9]. Diagnosis: incisional biopsy ^[9]. Must be distinguished from eczema of the nipple — eczema is typically bilateral, Paget's is unilateral.
  • Inflammatory breast cancer (T4d): Invasion of local lymphatic ducts → painful, swollen breast with cutaneous oedema involving at least 1/3 of the breast (peau d'orange) ^[5]. Can mimic mastitis — the key differentiator is failure to respond to antibiotics and the presence of skin biopsy showing dermal lymphatic invasion.
• Why carcinoma is hard and fixed: Malignant cells induce a desmoplastic reaction (fibroblast activation and collagen deposition) in surrounding tissue, creating a hard mass. The tumour invades Cooper's ligaments (→ skin tethering/dimpling), the pectoral fascia (→ fixation to chest wall), and lymphatics (→ peau d'orange).

• Who: Any age ^[4]
• Why important? Can mimic CA clinically and radiologically — presents as a spiculated mass on mammography ^[4]. The sclerotic stroma distorts the lobular architecture, making it look infiltrative.
• Management: Conservative or excision to rule out CA ^[4]. Core biopsy is essential.

• These enter the differential when there is pain, erythema, swelling, or warmth — features not typical of most breast cancers (except inflammatory breast cancer).
• Lactational mastitis: Lactating woman, first 3 months postpartum, S. aureus, responds to antibiotics ^[2][3].
• Periductal mastitis/abscess: Young smoker, subareolar, may have fistula ^[3].
• Idiopathic granulomatous mastitis: Young parous woman, hard irregular mass mimicking cancer, diagnosis of exclusion ^[3].
• Key trap: Inflammatory breast cancer can mimic mastitis. Always consider this if a "mastitis" in a non-lactating woman fails to respond to antibiotics, or if a lactating woman does not improve within 48–72 hours.

• Superficial sclerosing thrombophlebitis → palpable subcutaneous cord along the thoraco-epigastric vein ^[2].
• Self-limiting. Important mainly because the palpable cord can alarm the patient. Distinguished from other pathology by its linear, cord-like nature following the course of a superficial vein.

• The lecture slide notes "Others (skin lesions etc)" ^[1] as part of the DDx. Sebaceous cysts (epidermal inclusion cysts), accessory nipples, and dermatofibromas over the breast can all present as palpable "breast lumps."
• Key distinguishing feature: They are in the skin, not the breast parenchyma — they move with the skin, are superficial, and USG shows they arise from the cutaneous/subcutaneous layer.

1. Intraductal papilloma (most common cause) — friable fibrovascular core bleeds; solitary papilloma in large subareolar duct → single-duct bloody discharge
2. DCIS / Invasive ductal carcinoma — tumour erodes into duct; always exclude with mammography + core biopsy
3. Fibrocystic changes with active intraductal component — duct ectasia, intraductal hyperplasia, plasma cell mastitis ^[6]

The history systematically covers:

Mass characteristics:

• Onset and progression — How long has it been there? Getting bigger? (Rapid growth → phyllodes or malignancy)
• Cyclical changes / mastalgia — Does it change with the menstrual cycle? (Cyclical = likely fibrocystic changes)

Nipple symptoms:

• Discharge — Colour? Unilateral/bilateral? Single/multiple duct? Spontaneous/expressible? (Bloody + single duct + spontaneous = pathological → papilloma or cancer)
• Retraction — New onset? (Cancer, duct ectasia, periductal mastitis)

Skin changes:

• Itchiness, erythema, dimpling, peau d'orange ^[2] — suggest malignancy or inflammatory breast disease

Constitutional symptoms:

• Weight loss, bone pain, SOB ^[2] — suggest metastatic disease (bone, lung)

Risk factors for malignancy ^[2]:

• FHx: BRCA — any CA breast/ovary/prostate/pancreas
• PMHx: breast disease (e.g., DCIS), breast RT
• Oestrogen exposure: age of menarche, age of menopause, parity, breastfeeding, use of COC/HRT

Position: Patient at 45°, arms by sides, then raised above the head, then pressing on hips (contracts pectoralis — to reveal fixation to muscle).

Inspection:

• Size, symmetry, surgical scars (e.g., LN biopsy), skin changes (e.g., ulceration, dimpling, peau d'orange) ^[2]
• Nipple changes — the "5 D's": Deviation, Discolouration, Dermatitis, Depression (retraction), Discharge ^[2]

Why inspect with arms raised and then with hands on hips? Arms raised tenses the skin → makes dimpling and tethering more obvious. Hands on hips contracts pectoralis major → if the lump is fixed to the muscle, it will become less mobile or the skin over it will dimple.

Palpation of breast (start from the normal side) ^[2]:

• Comment on: site, size, shape, border, surface, consistency, tenderness, mobility (to skin and to muscle)
• Include the axillary tail of the breast

Palpation of axilla ^[2]:

• Groups: anterior (pectoral), posterior (subscapular), medial (chest wall), lateral (humeral), apical
• Comment: number, site, size, consistency, tenderness, fixation

Additional examination:

• Examine the contralateral breast (synchronous bilateral disease?)
• Examine the supraclavicular fossa (supraclavicular lymphadenopathy = advanced disease)
• Examine the liver (hepatomegaly → liver metastasis) ^[3]
• Examine the spine/bones (tenderness → bone metastasis) ^[3]

"Gold standard" for breast imaging and screening ^[2]. Uses low-dose X-rays to produce high-contrast images of the breast tissue.

Standard Views ^[2][3]:

• Craniocaudal (CC) view — X-ray beam travels top-to-bottom. Shows medial-to-lateral extent of the breast. Used to localize masses as inner vs. outer quadrant.
• Mediolateral oblique (MLO) view — X-ray beam travels at ~45° from superomedial to inferolateral. Includes the axillary tail, axillary lymph nodes, and upper outer quadrant in detail. The pectoralis major muscle should be visible to the level of the nipple to confirm adequate positioning.

CC view → outer vs inner quadrant; MLO view → upper vs lower half of the breast (the dividing line is perpendicular to pectoralis major) ^[2].

Advantages ^[2]:

• Gold standard — high sensitivity for calcifications (which USG cannot detect)
• Less operator-dependent than USG
• Can be used for annual screening
• Safe even in pregnant women (with abdominal shielding)

Limitations ^[2][3]:

• Cannot make a definitive diagnosis — can only depict a mass as abnormal or suspicious ^[3]
• Obscuration by dense breast tissue — in young women, dense parenchyma can mask lesions ^[3]
• Limited ability to visualize the chest wall and axilla (better on MLO view)
• Radiation exposure (though very low dose)

Mammographic Abnormalities to Look For ^[3]:

Why are microcalcifications important? Microcalcifications ( < 0.5 mm) often represent calcium deposits within areas of necrosis or active secretion in neoplastic cells. DCIS classically presents as clustered pleomorphic microcalcifications on mammography. Benign calcifications tend to be large, coarse, round, and uniform — they represent degenerative or vascular calcification.

Condition-Specific Mammographic Findings:

BI-RADS is the standardized reporting system used for both mammographic and ultrasound findings ^[3][11][13]. It converts imaging findings into a management recommendation. From the lecture slide ^[13]:

"Mammogram Reporting: BIRADS"

• Category 0: need further investigations
• Category 1: normal
• Category 2: benign
• Category 3: probably benign ( < 2% malignant)
• Category 4: suspicious of malignancy
• Category 5: highly suggestive of malignancy 95%
• Category 6: malignancy proven with biopsy

Expanded with management ^[3][6]:

Why is BI-RADS 3 managed with follow-up rather than biopsy? Because the malignancy risk is only 1–2%. Performing biopsies on all BI-RADS 3 lesions would subject a huge number of women to unnecessary invasive procedures. Instead, short-interval imaging (typically 6 months) monitors for any change. If the lesion is stable at 24 months, it is downgraded to BI-RADS 2. If it grows or changes, it is upgraded to BI-RADS 4 and biopsied.

USG should be performed for ALL patients presenting with a breast complaint ^[2]. It is the first-line imaging in young women ( < 35), pregnant, or lactating women because there is no radiation and the dense glandular tissue of young breasts is better penetrated by ultrasound than X-rays.

Roles of USG ^[2][3]:

• Distinguish cysts from solid lesions — this is the single most important role. A simple cyst on USG needs no further investigation.
• Improved sensitivity and specificity combined with mammogram, especially in young women with dense breast tissue ^[2]
• Guide FNAC, biopsy, and clipping before neoadjuvant chemotherapy ^[2]
• Assess axillary lymph nodes ^[2] — look for loss of fatty hilum (suspicious for metastasis)
• Identify presence of a prominent vascular supply (Doppler)
• Characterize solid masses as likely benign or malignant

Limitations ^[2][3]:

• Operator-dependent
• Cannot pick up most calcifications (microcalcifications are virtually invisible on USG) ^[2]
• NOT useful as a screening tool on its own ^[2]

USG Features — Benign vs. Malignant ^[3]:

Suspicious features on USG: "SHIT CME" — a mnemonic for: Spiculated margins, Hypoechoic, Irregular shape, Taller-than-wide, Calcification (internal), Microlobulation, Enhancement (posterior shadowing or central vascularity) ^[2]

Suspicious lymph node: loss of fatty hilum ^[2] — normal axillary lymph nodes have an echogenic fatty hilum. When this is replaced by hypoechoic cortical thickening, suspect metastatic infiltration.

Condition-Specific USG Findings:

Not routinely performed in the work-up of an undiagnosed breast mass ^[3][2]. Has high sensitivity but low specificity — meaning it finds almost everything, but many of those findings turn out to be benign, leading to unnecessary biopsies ^[2].

Indications for Breast MRI ^[3][2]:

• Equivocal results from mammogram or ultrasound
• Assessment of patients with breast implants (silicone implant rupture evaluation)
• Identify patients with clinically occult tumour presenting with positive axillary lymph nodes (unknown primary)
• Suspected multicentric or bilateral malignancy, especially invasive lobular carcinoma (ILC) — ILC is notorious for being underestimated on mammography because it grows in a diffuse, infiltrative pattern without forming a distinct mass
• Determine extent of disease accurately, especially chest wall involvement
• Identify extent of residual disease after excision showing positive margins
• Pre-operative evaluation to improve surgical planning
• Monitor results of neoadjuvant therapy
• Screening in high-risk patients (genetic predisposition — e.g., BRCA carriers)

MRI Features Suggestive of Malignancy ^[3]:

• Spiculated or irregular margins
• Rim-like enhancement
• Heterogeneous internal enhancement
• Enhancing internal septa
• Rapid uptake of contrast — nearly all invasive breast carcinomas enhance on gadolinium-contrast MRI (but some benign lesions also enhance, hence the low specificity)

• Uses a 21–23 gauge needle — no local anaesthesia needed ^[6]
• Provides a cytological diagnosis (individual cell morphology)
• Cannot assess tissue architecture — therefore cannot distinguish carcinoma in situ from invasive carcinoma ^[6]. This is a critical limitation.

Best used for:

• Cystic lesions — aspiration is both diagnostic and therapeutic ^[6]
• Low-risk presentations (e.g., non-palpable mass, equivocal mammogram)

Approach to FNAC of a Cyst ^[6]:

Why send blood-stained aspirate for cytology? Blood-stained fluid may indicate an intracystic papilloma or intracystic carcinoma. The blood comes from a vascular solid component within the cyst that has been disrupted by the needle.

• Uses a 9–14 gauge needle with local anaesthesia ^[6]
• Provides a histological diagnosis — can assess:
  • Tissue architecture (is it in situ or invasive?)
  • Tumour grading
  • Receptor status (ER/PR/HER2) ^[6]
• Performed if BI-RADS ≥ 4 ^[6]

Guidance methods for non-palpable lesions ^[6]:

• USG-guided — for masses visible on ultrasound
• Stereotactic (X-ray guided) — for microcalcifications visible only on mammography
• Tomosynthesis-guided (3D mammogram) — uses multiple X-ray angles
• MRI-guided — for lesions seen only on MRI

Enhanced technique: Vacuum-assisted core biopsy (VACB) — uses suction to pull tissue into the needle bore, obtaining larger and more representative samples. Increases yield compared to standard core biopsy ^[6].

Condition-Specific Histological Findings on Core Biopsy:

Indicated when core biopsy reveals a suspicious lesion but is not diagnostic — i.e., there is clinical-pathological discordance, or the core shows atypia that may underrepresent the true pathology ^[6][3].

Localizing Non-Palpable Lesions for Excisional Biopsy ^[6]:

When a lesion is non-palpable (detected only on imaging), the surgeon needs guidance to find it during surgery. Several localization methods exist:

• Indication: Pathological nipple discharge (unilateral, single-duct, bloody/serous) when the triple assessment does not identify a clear mass ^[2]
• Technique: A fine cannula is inserted into the discharging duct orifice at the nipple → contrast is injected → mammographic images taken
• Findings: Filling defect within the duct = intraductal papilloma or intraductal carcinoma; duct irregularity or cutoff = suspicious for malignancy
• Limitation: Technically challenging; success depends on identifying the correct duct

• Direct visualization of the inside of the duct using a microendoscope ( < 1 mm diameter)
• Can visualize and sometimes biopsy intraductal lesions
• Not widely available; mainly in specialized centres

• Smear of nipple discharge on a glass slide → stain → examine for malignant cells
• Low sensitivity — a negative result does not exclude malignancy
• Useful as an adjunct but never as a sole investigation

Why is management conservative? FBC is a physiological aberration of the hormonal cycle, not a true disease. Non-proliferative FBC confers NO increased cancer risk ^[3]. The goal is symptom relief.

When to investigate further: If there is a dominant palpable mass within the background of fibrocystic changes, it must undergo triple assessment to exclude a cancer hiding within the FBC.

The management of breast cysts is beautifully algorithmic:

The key decision: observe or excise?

The management hinges on size, symptoms, growth, and subtype ^[3][5]:

The lecture slide explicitly states ^[15]:

"Treatment: Microdochectomy — Excision of the diseased duct — Usually guided by ductogram / ductoscopy"

Why not just observe a papilloma? Because (a) the bloody discharge is distressing to the patient, (b) the papilloma carries a slight increased risk of malignancy (1.5–2×), and (c) you cannot be 100% certain the discharge isn't from a coexisting DCIS without excising and examining the entire duct.

Contraindication to observation: Multiple papillomas (diffuse papillomatosis) carry a higher cancer risk and should be excised.

Why is surgery rarely needed? Duct ectasia is an involutional process — the ducts dilate, accumulate secretions, and may cause transient symptoms. As involution completes, the process burns itself out. Surgery is only for persistent, bothersome symptoms.

This is a recurrent condition in young, smoking women. The management is stepwise but the key is that definitive cure requires excision of the diseased duct.

Why is total duct excision sometimes needed? If the abscess and fistula have affected multiple ducts (not just one), excising a single duct won't prevent recurrence from adjacent diseased ducts. Total (major) duct excision removes all the subareolar ducts and is definitive.

IGM is unique in that surgical excision is NOT recommended ^[3]. This is counterintuitive — you have a hard mass that mimics cancer, so the instinct is to "cut it out." But surgery in IGM leads to slow wound healing, fistula formation, and recurrence because the underlying granulomatous inflammation persists at the wound margins.

The single most significant complication of certain benign breast diseases is malignant transformation or, more accurately, the increased risk of subsequent breast cancer development. This is not a direct transformation in most cases, but rather a marker of genomic instability in the breast epithelium that predisposes to cancer elsewhere in either breast ^[3][7].

Why does atypia matter so much? ADH and ALH cells have begun to lose normal growth control — the nuclei are monomorphic and the architecture is abnormal. They have accumulated some (but not all) of the genetic hits needed for full malignant transformation. One more "hit" (e.g., loss of a tumour suppressor) can tip them over into DCIS or invasive cancer. This is the classic multi-hit model of carcinogenesis.

Lactational mastitis → Breast abscess ^[3][4]:

• Progresses to abscess formation in ~25% of patients ^[3]
• Why? Bacteria proliferating in stagnant milk → focal collection of pus walled off by inflammatory tissue. The abscess is often NOT fluctuant early on because it sits deep within the breast parenchyma surrounded by oedematous, indurated tissue ^[3].
• Abscess complications: If left untreated — pressure necrosis of overlying skin → spontaneous rupture → chronic draining sinus → cosmetic deformity and prolonged wound healing.

Periductal mastitis → Subareolar abscess → Mammary duct fistula ^[3]:

• This is a recurrent cycle in smokers:
  1. Smoking → toxic metabolite damage → squamous metaplasia of duct epithelium → duct obstruction
  2. Obstruction → secondary infection (mixed anaerobes + staph) → periductal inflammation
  3. Inflammation → subareolar abscess
  4. Abscess drains (spontaneously or by I&D) but the underlying diseased duct is not excised
  5. → Recurrence → periareolar fistula (communication between the diseased duct and periareolar skin) ^[3]
  6. → Chronic draining sinus → cosmetic deformity, chronic pain, social embarrassment

Why does the fistula keep recurring? Because the root cause is the diseased duct with squamous metaplasia. Simply draining the abscess removes the pus but leaves the obstructed, metaplastic duct in place. The duct will obstruct again → re-infect → re-abscess → re-drain at the same site. Definitive cure requires fistulectomy ± total duct excision + smoking cessation ^[3].

• Periductal mastitis and breast abscess — blocked dilated ducts predispose to secondary infection ^[3]
• Nipple retraction — progressive periductal fibrosis shortens the duct, tethering and inverting the nipple ^[3]. This is usually irreversible once established.
• Chronic nipple discharge — persistent creamy, multicoloured discharge can be socially distressing

• Recurrence — cysts can recur after aspiration, requiring repeat aspiration or surgical excision ^[4]
• Intracystic pathology — rarely, a cyst may harbour an intracystic papilloma or intracystic carcinoma (solid component within the cyst wall). This is why blood-stained aspirate or a residual mass after aspiration mandates core biopsy ^[4][6].

• Draining sinuses and chronic abscesses — the granulomatous inflammation can necrotise centrally and form chronic sinus tracts
• Cosmetic deformity — large inflammatory masses can distort the breast
• Rebound inflammation on steroid tapering — discontinuation or tapering of corticosteroids is associated with rebound inflammation ^[3]
• Slow wound healing if surgery is attempted — surgical excision of IGM is often followed by slow wound healing ^[3], fistula formation, and poor cosmesis

Although axillary lymph node dissection (ALND) is primarily performed for malignant disease, it is relevant to benign breast disease because: (a) SLNB may be performed with mastectomy for DCIS (to account for the possibility of occult invasive cancer found on final pathology) ^[7], and (b) students must know the complication profile to understand why ALND is NOT indicated for Phyllodes tumour ^[3].

The lecture slides detail these complications ^[18][19]:

"Axillary dissection: Removal of level I & II lymph nodes. Pectoralis minor as the landmark. Preservation of (special caution to): Long thoracic nerve, Thoracodorsal nerve, Intercostobrachial nerves." ^[18]

"Complications: Lymphedema (up to 10–20% risk), Nerve injuries, General surgical complications (skin infection, scar etc), Frozen shoulder" ^[18]

Adjuvant radiotherapy is used for borderline/malignant phyllodes tumour and (in the context of breast cancer) after breast-conserving surgery. The lecture slide lists ^[20]:

"Complications from radiation: Skin burn — preventable with radiogel, Infection, Lung fibrosis, Heart, Lymphoedema, Skin discoloration, Sternal necrosis"

While breast implants are primarily used in the context of breast cancer reconstruction, they are relevant here because mastectomy may be performed for benign disease (e.g., phyllodes tumour with inadequate margins, or prophylactic mastectomy in high-risk patients). The complications are ^[17]:

Why does BIA-ALCL occur? The exact mechanism is debated, but chronic inflammation around the implant (especially textured implants) creates a microenvironment of persistent T-cell activation. Over years, this chronic stimulation can lead to clonal expansion of aberrant T cells → lymphoma. It is exceedingly rare (estimated 1 in 10,000–30,000 implants) but has led to the withdrawal of certain textured implant brands.