GC012 Abnormal Lung Shadow On Chest Radiograph CXR, CT
An incidental or symptomatic radiographic finding on chest X-ray or CT scan representing a localized or diffuse opacity that requires systematic evaluation to determine its etiology, which may include infection, malignancy, inflammation, or vascular abnormality.
Abnormal Lung Shadow on Chest Radiograph (CXR, CT)
This GC lecture from HKU's Department of Diagnostic Radiology is fundamentally about what to do when you see something abnormal in the lung on a chest X-ray — and specifically, how to decide whether it's benign or malignant, how to characterize it, how to stage lung cancer, and how to approach diffuse lung disease. It is a radiology-oriented lecture, but it is deeply clinical because every imaging finding drives a management decision.
The lecture is structured around two major categories:
- Focal lung lesions — especially the solitary pulmonary nodule (SPN) and lung cancer
- Diffuse lung lesions — interstitial lung disease, infections (PJP, TB), bronchiectasis, emphysema
You are expected to walk away knowing how to describe a lung shadow, how to use CT (contrast CT, HRCT, PET-CT) appropriately, and when to biopsy. This lecture directly feeds into exam questions about lung nodule workup, benign vs malignant features, CT staging, and the role of ancillary investigations.
Learning Objectives (from the slides):
1. Describe abnormal lung shadow on CXR 2. Understand the clinical applications of various CT techniques 3. Understand the values of other ancillary investigations [1]
Slide-era algorithm versus current practice
The original flowchart teaches the enduring principles—compare priors, look for growth, then characterise with CT—but its fixed “2 years = benign” and universal “3–6 month follow-up” branches are too simple for clinical use. Management now depends on whether a nodule is solid or subsolid, exact CT size/volume, morphology, growth, patient risk and whether it arose incidentally or in a screening programme. [10,11]
Part 1: Focal Lung Lesions
The slide defines a solitary pulmonary nodule as a focal lung lesion < 3 cm in diameter. [1]
The conventional radiological definition is a rounded opacity up to 3 cm, surrounded by aerated lung and not accompanied by atelectasis, hilar enlargement or pleural effusion. A lesion > 3 cm is a mass and carries a substantially higher malignancy probability.
This is the bread-and-butter of lung radiology questions. The clinical scenario in the lecture is a 25-year-old asymptomatic, non-smoking man with an incidental SPN on CXR. The key question is: is this benign or malignant?
Why does the size matter?
- Up to 3 cm = "nodule" → management depends on CT phenotype, size, growth and clinical risk
- Above 3 cm = "mass" → treat as suspicious until an appropriate diagnostic pathway establishes otherwise
Why does age matter?
- In a 25-year-old non-smoker, the pre-test probability of malignancy is very low. The Fleischner incidental-nodule tables specifically do not apply below age 35; such patients need individual clinical/radiological review rather than automatic serial CT. [10]
- In a 65-year-old smoker, the same nodule carries a much higher probability of lung cancer.
SPN Workup Algorithm: What the Slide Is Teaching
Step 1: Check previous CXR
- No growth over 2 years → Benign
- Interval growth → Suspicious → CT scan
- No previous CXR → CT scan ± Bronchoscopy ± Sputum analysis [1]
Current qualifier: two-year stability is reassuring mainly for a well-measured solid nodule. Subsolid nodules may grow much more slowly and, when surveillance is indicated, may require up to 5 years. For an indeterminate nodule first detected on radiograph, the appropriate next imaging study is generally thin-section CT chest without IV contrast, not routine sputum analysis or bronchoscopy. [10,11]
CT thorax is used to:
- Characterize the lesion
- Determine solitary vs multiple nodules
- Stage a malignant lesion [1]
Hounsfield Units (HU) — First Principles
CT measures density or attenuation value of structures in Hounsfield Units (HU) [1]
| Substance | HU Value |
|---|---|
| Air | -1000 |
| Fat | approximately -50 to -100 |
| Water | 0 |
| Soft tissue | 30–50 |
| Calcification | > 150 |
Why does this matter? CT attenuation helps reveal composition:
- The slide’s region of interest measures -55 HU, demonstrating macroscopic fat and strongly favouring a hamartoma. [1]
- Diffuse, central, laminated or “popcorn” calcification usually supports a benign healed granuloma/hamartoma pattern.
- Soft-tissue attenuation is non-specific. HU varies with scanner, reconstruction, partial-volume averaging and placement of the measurement region; interpret it with morphology and growth.
Fat-containing nodule at -55 HU = Hamartoma [1]
High Yield Exam Point
A hamartoma is a common benign lung tumour containing variable fat, cartilage and connective tissue. Macroscopic fat and/or “popcorn” calcification is highly characteristic; the lecture image demonstrates a -55 HU fat-containing focus.
1.3 Nodule Characteristics on CT
Key characteristics to evaluate:
- Shape: round, lobulated
- Margins: smooth or spiculated
- Calcification: uniform, central, speckled, eccentric
- Fat content
- Cavitation
- Air bronchograms [1]
| Feature | Benign | Malignant |
|---|---|---|
| Margins | Well circumscribed, smooth | Ill-defined, spiculated |
| Calcification | Central, uniform | Eccentric calcification |
| Fat | Fat-containing | No fat |
| Shape | Polygonal/triangular | Irregular, lobulated |
| Position | Subpleural | N/A |
| Dynamic contrast enhancement (historical test) | Minimal enhancement is reassuring | Enhancement is suspicious but non-specific |
| Other | — | Pleural retraction, heterogeneous |
Source: [1]. These are probability modifiers, not verdicts: benign disease can be spiculated or FDG-avid, and cancers can be smooth, non-avid or partly calcified.
Why are spiculated margins malignant? Spiculations represent tumour cells infiltrating along interlobular septa, lymphatics, and alveolar walls. This "sunburst" or "corona radiata" appearance is the tumour reaching out into surrounding lung tissue — a classic sign of invasive growth.
Why is eccentric calcification suspicious? In benign lesions (granulomas), calcium deposits centrally or uniformly because the inflammatory process is concentric. In malignant lesions, calcification may be eccentric because the tumour engulfs a pre-existing calcified granuloma, or it represents dystrophic calcification in necrotic tumour tissue — the calcium is off-center.
Why does pleural retraction raise concern? Fibrosis/desmoplastic reaction around an invasive lesion can tether the visceral pleura, as the arrows show. Scar and inflammatory disease can also retract pleura, so the sign is not specific.
High Yield
An intrapulmonary lymph node typically lies close to a fissure or pleural surface and is solid, smooth, oval/lentiform or triangular. The slide’s red arrow points to this classic perifissural morphology. [1,12]
Benign nodule DDx:
- Granulomata (most common — TB, fungal)
- Inflammatory/Infectious lesions
- Arteriovenous malformations
- Hamartoma (fat)
- Adenoma [1]
Cavitating lesion DDx — history and clinical presentation are important:
- Abscess: pyrexia, cough
- Infarction: haemoptysis, chest pain, SOB
- Tumour: weight loss, haemoptysis [1]
Why do lesions cavitate? Central necrosis occurs in:
- Abscess: liquefactive necrosis from infection, contents drain via bronchus, leaving an air-fluid level
- Tumour: central ischaemic necrosis in rapidly growing tumours that outgrow their blood supply (especially squamous cell carcinoma)
- Infarction: coagulative necrosis from vascular occlusion (PE), the infarcted tissue breaks down
The slide deliberately gives only three clinical buckets. A complete differential also includes tuberculosis, fungal infection, septic emboli, granulomatosis with polyangiitis, rheumatoid nodules and cystic/cavitating metastases. Number, distribution, wall, surrounding consolidation/tree-in-bud change and the time course are as important as wall thickness.
Exam Trap
Not all cavities are cancer. A febrile patient with an air–fluid level may have an abscess; a smoker with a spiculated cavitating mass raises concern for squamous carcinoma. No single wall-thickness cutoff is diagnostic, and infection and tumour can coexist.
When a nodule does not have a definitive benign pattern, estimate malignancy probability from patient risk + thin-section CT size/type + morphology + growth.
Contrast enhancement on CT:
The paired pre/post-contrast image shows 20 HU enhancement, illustrating an older dynamic-enhancement test. Enhancement can occur in tumour and active inflammation and should not be used alone to label malignancy or dictate resection.
The slide’s options for an indeterminate nodule are close imaging follow-up, percutaneous or transbronchial biopsy, and resection. [1]
Current selection: exact follow-up interval is not universally 3–6 months. Small low-risk nodules may need no follow-up; larger, growing, part-solid or morphologically suspicious nodules may need short-interval CT, PET-CT, tissue sampling or definitive management. Use the appropriate incidental-nodule or screening framework and multidisciplinary judgement. [10–12]
CT-guided lung biopsy image: the needle traverses the posterior chest wall into a peripheral apical lesion under CT guidance. This route is useful for selected peripheral lesions; pneumothorax and pulmonary haemorrhage are key complications. Bronchoscopic sampling may be preferred for a bronchus sign, central target or when simultaneous nodal staging is needed.
Part 2: Lung Cancer (Lung Mass)
65-year-old man, smoker > 20 years, presenting with 2 months of haemoptysis and SOB [1]
This is the classic lung cancer presentation. The lecture shows:
Further evaluation of suspected lung cancer:
- CT scan: staging ± biopsy
- Bronchoscopy: biopsy + BAL
- Post-bronchoscopy sputum analysis [1]
Current sequence: obtain a contrast-enhanced chest CT including lower neck, liver and adrenals before biopsy when lung cancer is suspected, then choose the investigation that yields diagnosis and stage with the least risk. Sputum cytology now has a narrow role—mainly a central lesion when bronchoscopy or another invasive test is declined or not tolerated—not a routine post-bronchoscopy step. [13]
Contrast CT thorax introduces TNM staging:
- T — Primary tumour: size, location, invasion
- N — Nodal involvement: hilar, mediastinal, contralateral
- M — Metastasis: liver, adrenal, bone, brain [1]
Stage with the current edition
The slide correctly teaches the T–N–M domains but not a durable numeric stage table. Lung-cancer TNM changes over time; the IASLC ninth edition was published in 2025. Use the current local staging manual/reference card rather than memorising an older generated table. [15]
Why contrast? Contrast CT uses volumetric (spiral) scans with IV contrast [1]. IV contrast enhances blood vessels and allows differentiation between:
- Tumour and collapsed lung (collapsed lung enhances more uniformly)
- Tumour and mediastinal structures (to assess invasion)
- Lymph nodes and blood vessels
Modern CT scanners produce 0.5–0.625 mm slices for contrast CT thorax. [1]
Ancillary findings on CT: other nodules, lymph nodes, etc. [1]
The arrowed image shows a low-attenuation necrotic subcarinal lymph node, a highly suspicious mediastinal nodal finding. CT morphology/size cannot by itself establish pathological N stage; PET-CT and tissue sampling are often required if nodal status changes treatment. [1,13]
Pancoast tumour image: erosion of a rib and left transverse process, with extension into posterior soft tissues [1]
The lecture CT image demonstrates a posterior/paravertebral soft-tissue mass with arrows highlighting rib erosion, left transverse process erosion, and soft-tissue extension posteriorly [1].
Why is this important? A Pancoast (superior sulcus) tumour is a lung cancer at the apex of the lung that invades:
- Brachial plexus → arm pain, weakness, Horner's syndrome
- Ribs and vertebral bodies → bony destruction
- Sympathetic chain → Horner's syndrome (ptosis, miosis, anhidrosis)
- Subclavian vessels
High Yield
The lecture specifically emphasizes that MRI is superior for evaluating Pancoast (superior sulcus) tumours because it can delineate brachial plexus invasion and chest wall involvement better than CT. [1]
The lecture’s upper-abdominal CT demonstrates both liver and adrenal metastases. [1]
Bone, brain, liver and adrenal glands are important distant metastatic sites. An adrenal nodule in a patient with lung cancer is not automatically metastatic; dedicated CT/MRI characterisation or PET/tissue may be needed when the result alters management.
CT evaluation purposes:
- Stage disease — assess operability
- Radiation planning — anatomic relationship, disease extent, surrounding tissue thickness
- Assessing treatment response [1]
Pitfalls of CT:
- Mediastinal nodes: size criteria (nodes may be enlarged from inflammation, not metastases); microscopic metastases may be missed
- Indeterminate chest wall or mediastinal invasion [1]
Why is this a pitfall? A ≥10 mm short-axis node is radiologically enlarged, not histologically proven malignant. [13]
- Reactive nodes from infection/inflammation can be > 1 cm (false positive)
- Micro-metastases in normal-sized nodes are missed (false negative)
- This is why PET-CT and, when treatment depends on nodal status, systematic sampling with EBUS-TBNA and/or EUS-FNA are used. Surgical staging is reserved for selected cases, including persistently high suspicion after negative endosonography. [13]
Bronchoscopy approach depends on lesion location:
| Proximal Lesion | Peripheral Lesion | |
|---|---|---|
| Visualization | Directly visualized | Not visualized directly |
| Sampling | Saline washing and brushing (microbiology & cytology) | Bronchoalveolar lavage — BAL (microbiology & cytology) |
| Biopsy | Biopsy under direct vision (histology) | Guided transbronchial biopsy (histology) |
Source: [1]
Why the difference? Proximal endobronchial lesions can be seen and sampled directly. Peripheral lesions are not directly visible through conventional bronchoscopy; radial EBUS, fluoroscopy, virtual/electromagnetic navigation or robotic guidance may be used. BAL is valuable for selected infection/diffuse-disease questions but is not a reliable substitute for tissue diagnosis of every peripheral nodule.
Other staging techniques for lung cancer:
- Transoesophageal ultrasound + biopsy — an endoscope with an ultrasound probe is passed through the oesophagus to visualise and biopsy adjacent mediastinal lymph nodes (EUS-FNA) [1]
- Mediastinoscopy + biopsy — a mediastinoscope is introduced through an incision at the base of the neck and advanced alongside the trachea to examine and sample mediastinal lymph nodes; an anterior mediastinotomy (Chamberlain procedure) is an alternative approach [1]
- Thoracotomy + nodal sampling — the pleural cavity is entered through a limited incision (e.g., 5th intercostal space) to remove the lung mass and sample enlarged lymph nodes (e.g., aortico-pulmonary window nodes) [1]
- PET-CT [1]
Modern order: PET-CT defines suspicious nodal/distant targets; EBUS-TBNA/EUS-FNA are generally the first invasive mediastinal staging tests. Mediastinoscopy remains valuable when endosonography is negative but clinical suspicion is high. Open thoracotomy purely for initial nodal diagnosis is no longer the routine starting point. [13]
MRI:
- Similar limitations to CT
- Expensive
- Superior for superior sulcus (Pancoast) tumours — evaluates chest wall and brachial plexus invasion [1]
Why MRI for Pancoast? MRI has excellent soft tissue contrast and can image in multiple planes (coronal, sagittal). This is critical for delineating the relationship between tumour and the brachial plexus, subclavian vessels, and vertebral bodies — all of which influence surgical planning.
PET/CT uses 18-fluoro-2-deoxy-D-glucose (18-FDG):
- Based on glucose metabolism
- Neoplasms and inflammatory lesions show increased metabolic activity (hot) Advantages:
- Whole body scans — detect occult metastases elsewhere
- The slide quotes high sensitivity (90–95%) Disadvantages:
- Lower specificity — false positives [1]
Why false positives/negatives? FDG uptake is not cancer-specific: infection, granulomatous disease and recent intervention can be avid. Small lesions, indolent/lepidic or mucinous tumours, hyperglycaemia and motion can reduce detection. Therefore the slide’s 90–95% figure is context-dependent, and a PET-positive mediastinal node normally needs pathological confirmation before curative treatment is denied. [13]
Past Paper Alert – 2025 MCQ Q41
"A 78-year-old male with a 3cm lung mass, bone pain — what is the MOST EFFECTIVE imaging to investigate further?" Answer within the listed options: whole-body PET-CT, because it can demonstrate metabolically active nodal, bone and other distant disease. DEXA measures bone density, while chest MRI and ultrasound do not provide whole-body staging. Clinical-pathway caveat: with only an abnormal CXR and no cross-sectional imaging, current guidance obtains contrast-enhanced staging CT before deciding on PET-CT and the safest biopsy target. [3,13]
Part 3: Diffuse Lung Lesions
Diffuse lesions affect:
- Interstitium
- Airspace
- Small airways [1]
Diffuse lesion DDx:
- Interstitial lung disease (interstitial pulmonary fibrosis, occupational lung disease)
- Infections (the slide uses the historical name Pneumocystis carinii; the human pathogen is Pneumocystis jirovecii), TB
- Bronchiectasis and bronchiolitis
- Emphysema [1]
54-year-old lady, increasing SOB, painful joints, non-smoker [1]
The combination of ILD + painful joints should make you think of connective tissue disease-associated ILD (e.g., rheumatoid arthritis, systemic sclerosis, polymyositis/dermatomyositis with anti-Jo-1 antibody) [4].
CXR findings:
CXR of ILD:
- Lower zone predominance
- Reticular shadowing
- Volume loss
- Shaggy heart borders [1]
The lecture CXR demonstrates bilateral diffuse reticular opacities, most conspicuous in the lower/peripheral lungs, with reduced lung volumes and indistinct (“shaggy”) cardiac borders. The associated painful joints make connective-tissue-disease-associated ILD an important clinical hypothesis, not an image-only diagnosis. [1]
Why lower zone? Idiopathic pulmonary fibrosis (UIP pattern) and many CTD-associated ILDs have a basilar and peripheral predominance. The "shaggy heart borders" occur because fibrotic changes blur the normally sharp cardiac silhouette (similar to how a shaggy sweater has fuzzy edges). Volume loss occurs because fibrosis contracts and shrinks the lung tissue.
Exam Discriminator
Distribution narrows the differential but is not absolute. Upper-lung-predominant fibrosis suggests entities such as sarcoidosis or some pneumoconioses; basal/subpleural fibrosis suggests UIP/IPF, asbestosis or CTD-ILD. Always integrate axial distribution, airway/nodule/cyst pattern, exposure and serology.
HRCT:
- Old protocol: 1 mm sections at 10 mm intervals (high resolution with reduced radiation)
- Modern scanners: 0.5–0.625 mm contiguous source slices
- Additional expiration and prone images can be acquired
- Excellent for studying lung parenchyma, interstitium, and airways [1]
Modern interpretation: “HRCT” is a thin-section acquisition/reconstruction technique, not a different scanner and not necessarily three complete series. Volumetric inspiratory thin sections are the core; expiratory imaging is added when air-trapping is relevant, and limited prone imaging when dependent basal opacity might mimic disease. Protocol and dose are tailored to the question.
Why prone imaging? Dependent posterior atelectatic opacity may clear in prone position; persistent abnormality supports genuine parenchymal disease. “Clears = dependent” is helpful, but persistence and morphology still require radiological interpretation.
Why expiratory imaging? Air trapping (seen in small airway disease, bronchiolitis obliterans, early COPD) is best demonstrated on expiratory scans. Normal lung deflates and increases in density on expiration; trapped air remains dark.
Standard CT vs HRCT
| Feature | Standard Contrast CT | HRCT |
|---|---|---|
| Reconstruction | Often thicker soft-tissue and lung series for a mass/staging question | Contiguous thin-section, high-spatial-frequency lung reconstruction |
| Contrast | Often IV contrast for suspected cancer/staging | Usually non-contrast for diffuse parenchymal characterisation |
| Coverage | Volumetric whole thorax | Modern examinations are also volumetric; targeted expiratory/prone additions as indicated |
| Best for | Mass lesions, staging, vascular structures | Parenchymal, interstitial, and airway disease |
| Limitation | Thicker reconstructions can obscure fine interstitial detail | High image noise; an HRCT protocol is not a substitute for contrast staging/vascular protocols |
Standard CT vs HRCT — Key Visual Teaching Point
The paired slide contrasts a relatively unremarkable thicker-section lung image with a thin-section image displaying extensive bilateral basal/subpleural reticulation and stacked cystic spaces (honeycombing). The teaching point is the value of thin sections and an appropriate lung reconstruction/window, not that “standard CT” and HRCT are inherently different machines. [1]
HRCT in diffuse lesions:
- Characterize disease: assess for air-trapping; nodular, reticular pattern, honeycombing
- Determine extent of disease: upper/mid/lower; central/peripheral
- Localize site for biopsy
- Post-treatment evaluation [1]
What do these patterns mean?
| HRCT Pattern | What It Represents | Classic Disease |
|---|---|---|
| Reticular | Thickened interlobular septa, fibrosis | IPF, asbestosis |
| Nodular | Small discrete opacities | Sarcoidosis, miliary TB, silicosis |
| Honeycombing | Clustered cystic spaces with thick walls | End-stage IPF (UIP pattern) |
| Ground-glass opacity | Partial filling of alveoli or thickening of interstitium | PJP, NSIP, alveolar haemorrhage |
| Tree-in-bud | Small airway inflammation with plugging | Infectious bronchiolitis, TB |
| Cystic | Thin-walled air-containing spaces | LAM, LCH, PJP |
3.5 Specific Diffuse Diseases Shown in Lecture
- CXR image: hyperinflated lungs with diffuse fine reticular/cyst-related lucency and small bilateral pleural effusions/blunted costophrenic angles [1]
- CT image: innumerable bilateral, diffuse, round, relatively uniform thin-walled cysts with intervening lung—the visual pattern that distinguishes LAM from ordinary emphysema [1]
- Occurs almost exclusively in women, commonly during the reproductive years
- Associated with tuberous sclerosis complex
- CXR image: bilateral diffuse, fairly symmetric perihilar/interstitial-airspace opacity [1]
- CT image: widespread bilateral ground-glass opacity with scattered thin-walled cystic/pneumatocele-like lucencies [1]
- Classic in immunocompromised patients (HIV/AIDS with CD4 < 200)
- The lecture shows both LAM and PJP as examples of diffuse cystic/interstitial disease
- CXR: prominent bronchovascular markings with tubular/linear and ring-like lucencies representing dilated airways; the lecture highlights these findings in the right lower zone [1]
- CT: extensive bilateral bronchial dilatation with bronchial-wall thickening, ring-like/cystic airway structures, and clustered dilated bronchi with a cystic/saccular configuration in both central and peripheral lung regions [1]
- Key diagnostic signs: “signet ring” sign (bronchus larger than its accompanying artery), lack of normal airway tapering, and visible bronchi close to the pleural surface
- Distribution gives clues to aetiology (see table in section 3.2 above)
Past Paper Alert – 2020 MCQ Q75
"55-year-old lady with 2-year history of SOB, sputum production, haemoptysis. CXR shows streaky shadows with tramlines. What radiological investigation to confirm diagnosis?" Answer: HRCT thorax — tramlines on CXR suggest bronchiectasis, and HRCT is the gold standard for confirming bronchiectasis. NOT contrast-enhanced CT (that's for masses/staging), NOT PET-CT (that's for cancer staging), NOT V/Q scan (that's for PE). [5]
| CT Technique | When to Use | What It Shows | Key Points |
|---|---|---|---|
| Non-contrast CT | Nodule characterization, calcification, fat | Attenuation values (HU), density | No IV contrast needed |
| Contrast CT Thorax | Lung cancer staging, vascular assessment | Enhancement of masses, lymph nodes, vessels | 0.5–0.625 mm slices; TNM staging |
| HRCT | Diffuse lung disease, ILD, bronchiectasis | Parenchymal and interstitial detail | Inspiration + expiration + prone; no contrast |
| CT-guided biopsy | Indeterminate or peripheral nodules | Tissue for histology | Risk of pneumothorax |
| PET-CT | Staging potentially treatable lung cancer, selected indeterminate nodules | Metabolic activity plus CT anatomy | Size/histology dependent; infection/inflammation cause false positives |
Sources: [1,10–14]
Take Home Points:
- Focal or diffuse disease — the first discriminating question
- Choose the optimal imaging modality for the clinical scenario
- Know the suspicious imaging features for lung malignancy
- Understand the indications for lung biopsy
- Know other ancillary investigations and staging techniques [1]
Integration with Related Material
- Pleural shadows on CXR — asbestosis causes pleural plaques (calcified), pleural thickening, and mesothelioma. These are pleural (not parenchymal) shadows. ILD from asbestosis causes basilar fibrosis similar to IPF. [8]
- Haemoptysis + lung mass → contrast CT first, then choose bronchoscopy, EBUS/EUS, percutaneous biopsy or another accessible target according to lesion location and staging needs
- Haemoptysis + tramlines → bronchiectasis → HRCT
- Bilateral fine basal crackles with JVP not raised → think ILD/IPF (not heart failure because JVP normal) [9]
- Tramlines on CXR → bronchiectasis
- Stony dull percussion → pleural effusion (not related to parenchymal disease)
High Yield Summary
- Start by deciding focal versus diffuse, then compare every prior study.
- An indeterminate nodule on CXR usually needs thin-section non-contrast CT for true size, solid/subsolid type, morphology, multiplicity and composition.
- Two-year stability is reassuring for a solid nodule; subsolid nodules behave differently and may need longer surveillance.
- Fat and benign calcification patterns are reassuring; spiculation, growth, a solid component and pleural retraction raise risk. No single feature proves cancer.
- Follow-up, PET-CT, biopsy and resection are selected from nodule size/type, patient risk and estimated malignancy probability—not a universal 3–6 month rule.
- A lung mass/suspected cancer needs contrast CT before biopsy; choose a tissue target that also establishes the highest stage with least risk.
- PET-CT improves staging but inflammatory disease can be avid and some tumours are non-avid; confirm important nodal findings with EBUS/EUS-guided sampling.
- MRI is particularly useful for superior sulcus tumour extension into plexus/chest wall.
- Thin-section HRCT characterises diffuse parenchymal and airway patterns and their distribution; expiratory/prone additions are question-specific.
- Visual anchors: LAM = diffuse uniform thin-walled cysts; PJP = diffuse ground glass ± cysts; bronchiectasis = signet-ring/lack of tapering/visible peripheral bronchi.
Active Recall - Abnormal Lung Shadow on CXR/CT
[1] Lecture slides: GC 012. Abnormal lung shadow on chest radiograph CXR, CT.pdf [2] Senior notes: Ryan Ho Respiratory.pdf (Section 2.6 Abnormal Lung Shadows) [4] Senior notes: Block A - Rheumatology Interactive Tutorial.pdf (Case P2) [5] Past papers: 2020 Fourth Summative Assessment MCQ paper.pdf (Q75) [8] Lecture slides: GC 083. Shortness of breath in a construction site worker.pdf [9] Past papers: 2024 Fourth Summative MCQ.pdf (EMQ Q1–4) [10] MacMahon H, Naidich DP, Goo JM, et al. Guidelines for Management of Incidental Pulmonary Nodules Detected on CT Images: From the Fleischner Society 2017. Radiology. 2017;284:228–243. doi:10.1148/radiol.2017161659. [11] American College of Radiology. ACR Appropriateness Criteria: Incidentally Detected Indeterminate Pulmonary Nodule. Revised 2023. [12] American College of Radiology. Lung CT Screening Reporting & Data System (Lung-RADS), version 2022. (Use for screening CT; it is not interchangeable with incidental-nodule guidance.) [13] National Institute for Health and Care Excellence. Lung cancer: diagnosis and management (NG122), Diagnosis and staging. Updated March 2024. [14] Raghu G, Remy-Jardin M, Richeldi L, et al. Idiopathic Pulmonary Fibrosis (an Update) and Progressive Pulmonary Fibrosis in Adults: An Official ATS/ERS/JRS/ALAT Clinical Practice Guideline. Am J Respir Crit Care Med. 2022;205:e18–e47. [15] International Association for the Study of Lung Cancer. IASLC Staging Cards in Thoracic Oncology, 9th Edition and IASLC Staging Manual in Thoracic Oncology, 3rd ed. Published 2025.
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