GC077 Pleural Effusion In A Chronic Smoker
Accumulation of fluid in the pleural space in a chronic smoker, most commonly due to underlying malignancy (such as lung cancer or mesothelioma), though infectious, cardiac, and other etiologies must also be considered.
Pleural Effusion in a Chronic Smoker — Lung Cancer
Big Idea: A chronic smoker presents with pleural effusion. The differential diagnosis is broad, but in this clinical context the lecture takes you on a journey from understanding the pathophysiology of pleural fluid accumulation → to investigating the effusion → discovering it is exudative with atypical cells → pursuing tissue diagnosis → confirming lung cancer (specifically adenocarcinoma) → understanding staging, molecular testing, and the modern treatment landscape of non-small cell lung cancer (NSCLC). This is a classic "one symptom, one deadly diagnosis" lecture that threads together respiratory medicine, oncology, and data interpretation.
Learning Objectives [1]:
- Learn the pathophysiology, common causes and investigations of pleural effusion
- Understand the pathology and natural history of lung cancer, and cigarette smoking as the predominant cause
- Understand the symptoms and signs of lung cancer with reference to the anatomy of the thoracic structures and cancer metastasis
- Learn the principles of investigations, staging and treatment of lung cancer
M/64, chronic smoker, retired restaurant waiter [1]
- Presents with pleural effusion
- Diagnostic + therapeutic thoracentesis × 2
- Exudative changes
- Atypical cells with large nuclear-to-cytoplasmic (N/C) ratio — need to rule out malignancy
- Non-diagnostic pleural fluid cytology and percutaneous biopsy — meaning the initial cytology did NOT definitively show cancer, and even a percutaneous (needle) biopsy was non-diagnostic
This case illustrates a critical real-world point: pleural fluid cytology has imperfect, tumour-dependent sensitivity. When an adequate cytology sample is non-diagnostic but suspicion for malignancy remains high, choose the next tissue target from the imaging—often image-guided pleural biopsy/pleuroscopy, EBUS-TBNA or endobronchial biopsy—rather than assuming that repeated taps will settle the diagnosis [18].
Read the index radiograph (slides 3 and 32): there is a large right pleural effusion, with a curved upper fluid margin and only a small amount of aerated right upper lung remaining. The opacity occupies most of the right hemithorax and obscures the right hemidiaphragm/costophrenic angle. In a near-white hemithorax, always use volume effect to refine the differential: mass effect/contralateral shift favours a large effusion, whereas ipsilateral shift favours collapse; little shift may reflect a mixed process (for example, effusion plus obstructing-tumour atelectasis). A CXR demonstrates the syndrome, but ultrasound is required to confirm a safe fluid pocket and CT is used to assess the underlying lung and pleura.
Part 1: Pleural Effusion — Pathophysiology, Causes, and Investigation
The pleural space normally contains a tiny amount of fluid (~5–15 mL) that acts as a lubricant between the visceral and parietal pleura. The balance of fluid in this space depends on four key forces [1]:
| Force | Direction | Explanation |
|---|---|---|
| 1. Hydrostatic pressure | Drives fluid OUT of the vascular compartment INTO the pleural space | Like water pressure in a pipe — the higher the pressure, the more fluid leaks out. Elevated in heart failure. |
| 2. Oncotic pressure | Keeps fluid IN the vascular compartment | Proteins (mainly albumin) in the blood act like sponges, holding water inside vessels. Reduced in hypoalbuminaemia (cirrhosis, nephrotic syndrome). |
| 3. Lymphatic drainage | Removes fluid FROM the pleural space | Lymphatics on the parietal pleura absorb excess pleural fluid. Blocked by tumour, inflammation, or fibrosis. |
| 4. Capillary permeability | Controls leak rate | Increased permeability (inflammation, infection, malignancy) allows more protein and fluid to escape into the pleural space. |
Additionally, the lecture mentions small holes in the diaphragm [1] — these are actual anatomical fenestrations that allow communication between the peritoneal and pleural cavities. This explains:
- Hepatic hydrothorax in cirrhosis (ascitic fluid tracks up through diaphragmatic defects) [7]
- Peritoneal dialysis-related pleural effusion (PD fluid leaks into the thorax) [4]
Why do we get pleural effusion?
Pleural effusion = imbalance in Starling forces OR impaired lymphatic drainage OR increased capillary permeability OR fluid tracking from the peritoneum. The pathophysiology directly determines whether the effusion is transudative or exudative.
The slide also groups common mechanisms as follows [1]:
- Increased hydrostatic pressure: congestive heart failure, renal failure with fluid retention, and other volume overload states.
- Reduced oncotic pressure: cirrhosis, nephrotic syndrome, severe malnutrition, and other forms of hypoalbuminaemia.
- Increased capillary permeability: infection of the lung or pleura, collagen vascular disease, malignant pleural involvement, and intra-abdominal processes such as pancreatitis or liver abscess.
- Reduced lymphatic drainage: malignant infiltration of mediastinal, pulmonary, or pleural lymphatics, and necrotising or granulomatous infections.
Light's Criteria: Pleural fluid is EXUDATIVE if ANY ONE of the following is met [2]:
- Pleural fluid / serum protein ratio > 0.5
- Pleural fluid / serum LDH ratio > 0.6
- Pleural fluid LDH > 2/3 of upper limit of normal (ULN) of serum LDH
Why this matters from first principles:
- A transudate is caused by systemic factors (↑hydrostatic pressure or ↓oncotic pressure) — the pleural membranes themselves are healthy, so protein and LDH don't leak across. The fluid is "clear" and protein-poor.
- An exudate is caused by local pleural/lung disease (inflammation, infection, malignancy) — damaged capillaries or inflamed pleura leak protein and cellular enzymes (LDH) into the fluid. The fluid is protein-rich.
| Feature | Transudate | Exudate |
|---|---|---|
| Mechanism | Systemic ↑hydrostatic or ↓oncotic | Local pleural/lung disease |
| Common causes | Heart failure, cirrhosis, nephrotic syndrome, hypothyroidism, peritoneal dialysis | Malignancy, infection (pneumonia, TB, empyema), PE, connective tissue disease (RA, SLE), pancreatitis [2][6] |
| Protein | Low | High |
| LDH | Low | High |
Exam Trap: Light's Criteria
Light's criteria tend to overdiagnose exudates, especially in patients with heart failure who have received diuretics. If the fluid only just meets exudative criteria and the clinical picture still suggests a transudate, a serum–pleural albumin gradient > 1.2 g/dL or serum–pleural protein gradient > 3.1 g/dL supports a transudative mechanism. Do not reinterpret the ratios without the clinical context. [2]
Once you've confirmed the effusion is exudative, you need to narrow the cause:
| Test | Finding | Significance |
|---|---|---|
| pH | Low | Pleural infection, rheumatoid pleuritis, malignancy, TB or oesophageal rupture; in suspected infection, use the decision thresholds below rather than a generic <7.30 cut-off |
| Glucose | Low (lower than blood) | Same as low pH causes — organisms/cells consuming glucose |
| LDH | Markedly raised | Intense pleural inflammation or cell turnover; non-specific, so interpret with pH, glucose, imaging and clinical context |
| Cell count | Neutrophil predominant | Acute inflammation: parapneumonic, PE, abdominal disease |
| Cell count | Lymphocyte predominant | Chronic inflammation: malignancy, TB, RA/SLE [3] |
| Cytology | Malignant cells | Confirms malignant involvement; sensitivity varies greatly by tumour type, so a negative result does not exclude malignancy [18] |
| ADA | Raised | Supports TB pleuritis in the right epidemiological context, but is not a stand-alone diagnosis; BTS prefers pleural tissue for mycobacterial culture when TB is suspected [18] |
| Microbiology | Gram stain, AFB smear, culture | Bacterial infection, TB |
| Triglycerides / chylomicrons | Milky fluid with high triglycerides; chylomicrons confirm | Chylothorax from thoracic-duct damage or obstruction; high cholesterol instead suggests pseudochylothorax in a chronic effusion [22] |
| Amylase | Elevated | Pancreatitis, malignancy, oesophageal rupture |
| Bloody | Blood-stained fluid | Trauma, malignancy, PE and other causes; haemothorax specifically requires a pleural-fluid haematocrit > 50% of peripheral blood haematocrit [18] |
In the index case: exudative effusion + atypical cells with large N/C ratio → suspicion for malignancy [1]
Suspected pleural infection: act on pH, not appearance alone
If fluid is frankly purulent, treat as empyema and drain. If it is not purulent, measure pH promptly in a blood-gas syringe (avoid local-anaesthetic contamination) [18]:
| Pleural-fluid pH | Interpretation and action |
|---|---|
| ≤7.20 | High risk of complicated parapneumonic effusion/pleural infection → insert an intercostal drain if ultrasound confirms safely accessible fluid |
| > 7.20 to < 7.40 | Intermediate risk → check LDH; consider drainage if LDH > 900 IU/L, especially with ongoing fever, a large effusion, glucose ≤4.0 mmol/L, pleural enhancement on CT or septations on ultrasound |
| ≥7.40 | Low risk → no immediate drain solely on biochemistry; monitor and reassess if the patient fails to improve |
Step 1: Imaging
- CXR: Meniscus sign or blunted costophrenic angle (requires ~200 mL to be visible) [3]
- Thoracic ultrasound: More sensitive than CXR for small/loculated fluid, distinguishes fluid from consolidated lung and selects a safe aspiration site. Image guidance should always be used for thoracentesis [18][19].
- Contrast-enhanced CT if malignancy is suspected or the initial evaluation is non-diagnostic. PET-CT is principally a staging test once lung cancer is suspected/confirmed, or a selected problem-solving test—not a substitute for pleural tissue diagnosis.
Step 2: Diagnostic Thoracentesis
- Typical indication: a new undiagnosed effusion with a safe ultrasound window. Sampling may be deferred when a bilateral effusion is clinically typical of heart failure and responds to treatment; conversely, unilateral/asymmetric, febrile, pleuritic or non-resolving fluid needs investigation.
- Send simultaneously with blood sample (for paired protein/LDH ratios)
- Order tests according to the differential: paired protein/LDH, cell count and differential, pH/glucose when infection is possible, microbiology, and cytology. For suspected malignant pleural effusion, send 25–50 mL for cytology with direct smear and cell-block preparation; repeating small-volume taps is not a substitute for choosing the next best tissue test [18].
Step 3: If non-diagnostic
- Pleuroscopy (medical thoracoscopy) / image-guided pleural biopsy [1]
- EBUS-TBNA if mediastinal lymphadenopathy present
- Endobronchial biopsy if endobronchial lesion seen on bronchoscopy
The semi-rigid pleuroscope shown on slide 33 is handled like a flexible bronchoscope through a single port. Its key advantage is not the instrument itself but direct inspection of the pleural surface with targeted biopsies; pleural fluid can be drained and talc poudrage or an indwelling pleural catheter may be planned in the same procedural pathway.
| Scenario | Management principle |
|---|---|
| Effusion clinically typical of heart failure | Treat heart failure first; sample if unilateral/markedly asymmetric, febrile, pleuritic, atypical or non-responsive |
| Undiagnosed unilateral effusion | Investigate; do not insert a chest drain merely because it is unilateral. Perform ultrasound-guided diagnostic aspiration unless a more appropriate direct biopsy strategy has been chosen |
| Symptomatic free-flowing effusion | Slow therapeutic aspiration can assess symptom response and whether the lung re-expands |
| Malignant pleural effusion | Individualise between indwelling pleural catheter (IPC), talc pleurodesis and repeat aspiration according to symptoms, prognosis, patient preference and lung expandability; IPC is generally favoured for significant non-expandable lung [18] |
| Pleural infection/empyema | Antibiotics plus small-bore intercostal drainage when indicated by pus, microbiology or the pH-based pathway above [18] |
| TB pleurisy | Anti-TB treatment |
Pleural aspiration safety
Use thoracic ultrasound in the procedure position, enter just above a rib, and drain slowly by syringe or gravity rather than wall suction. For a therapeutic tap, BTS advises stopping for chest tightness, pain, persistent cough or worsening breathlessness and, in general, limiting a single attempt to 1.5 L [19].
Signs of pleural effusion [8]:
- Mediastinum shift AWAY (if large)
- Reduced chest wall movement
- Stony dullness on percussion
- Reduced vocal fremitus
- Reduced breath sounds
Additional nuance from senior notes [3]:
- Above the effusion: compressed lung → bronchial breathing + increased vocal resonance (Aegophony — "E to A" change)
- Below/at the effusion: fluid blocks sound → decreased breath sounds + decreased vocal resonance
Past Paper Alert: Signs of Pleural Effusion
The 2024 MCQ EMQ asked: "Stony dull percussion note" → answer is malignant pleural effusion (or any pleural effusion). The key discriminator from consolidation is that consolidation has increased vocal resonance/fremitus while effusion has decreased vocal resonance/fremitus. Both have dullness, but effusion is "stony" dull [9].
Part 2: Lung Cancer — The Diagnosis Behind the Effusion
Non-small cell lung cancer (NSCLC) = 85% of lung cancer [1]
| Feature | Male patients | Female patients (in Hong Kong) |
|---|---|---|
| Smoking | 80% are smokers | < 40% are smokers |
| Histology | Mixed | > 75% adenocarcinoma |
| Risk factors | Smoking, occupational | Environmental: passive smoking, diet, cooking fumes |
| Genetic: EGFR gene mutation — important in non-smoking patients with adenocarcinoma |
Why is this HK-specific data important? In Hong Kong (and East Asia generally), a large proportion of female lung cancer patients are non-smokers with adenocarcinoma harbouring EGFR mutations. This has enormous treatment implications — these patients respond well to EGFR-TKIs (targeted therapy). The lecture explicitly contrasts Eastern vs. Western lung cancer genetics [1].
The slide further contrasts the distribution of driver alterations [1]:
| Population | More prominent alteration shown |
|---|---|
| Western | KRAS 25–30%, EGFR 10–15% |
| Eastern | EGFR 50–60%, KRAS 5–10% |
EML4-ALK is shown at approximately 5% in both groups, with smaller proportions of MET, HER2, ROS1, RET, NRAS, BRAF, and PIK3CA alterations.
High Yield: Smoking and Lung Cancer
In Hong Kong: 80% of male lung cancer patients are smokers. Among females, < 40% are smokers, with > 75% having adenocarcinoma. EGFR gene mutations are important in non-smoking adenocarcinoma patients. [1]
The lecture's WHO classification slide is historical [1]. It is useful for recognising the major lineages, but labels such as bronchioloalveolar carcinoma (BAC) and “large-cell carcinoma” as a broad bucket pre-date current pathology classification. Current reports integrate morphology, immunohistochemistry and molecular findings.
I. Malignant Epithelial Tumours (the main ones to know):
| Type | Key Features | Association |
|---|---|---|
| Squamous cell carcinoma (epidermoid) | Central location, cavitation, keratin pearls | Strongest smoking association, ↑Ca²⁺ (PTHrP) |
| Small cell carcinoma (oat cell) | Central, highly aggressive, rapid growth | Strong smoking association, paraneoplastic syndromes (SIADH, Cushing's); usually systemic therapy ± thoracic RT, with surgery reserved for a rare, carefully staged very-early subset |
| Adenocarcinoma | Often peripheral; gland formation and/or mucin, with acinar, papillary, micropapillary, solid or lepidic patterns | Most common in never-smokers; test for actionable drivers |
| Large cell carcinoma | Peripheral, undifferentiated, diagnosis of exclusion | Poor prognosis |
| Adenosquamous carcinoma | Mixed features | Uncommon |
| Carcinoid tumour | Neuroendocrine, low-grade | Can cause carcinoid syndrome |
II. Malignant Mesothelial Tumours:
- Malignant mesothelioma — epithelial, fibrous (spindle cell), or biphasic subtypes [1]
- Associated with asbestos exposure (links to GC 083: construction site worker)
Pathogenesis of adenocarcinoma and squamous cell carcinoma differ — the visual sequence on slide 14 contrasts proximal-airway squamous carcinogenesis (normal epithelium → basal-cell hyperplasia → squamous metaplasia → dysplasia → carcinoma in situ → invasive squamous carcinoma) with peripheral adenocarcinoma precursors (atypical adenomatous hyperplasia → adenocarcinoma in situ → invasive adenocarcinoma) [1]. The slide's older term BAC should now be translated according to invasion: adenocarcinoma in situ, minimally invasive adenocarcinoma or a lepidic-predominant invasive adenocarcinoma. Slide 15's many different micrographs reinforce that pulmonary adenocarcinoma is morphologically heterogeneous—even within one tumour—so adequate tissue and modern subtyping matter.
2.3 Clinical Features — "Relating Symptoms to Anatomy"
The lecture emphasises that clinical presentation depends on where the tumour is and what structures it invades [1].
- A small proportion may have a radiological abnormality only (5%), without symptoms.
- Constitutional symptoms: malaise, reduced appetite, and weight loss.
- Bronchial mucosal ulceration → cough, sputum, and haemoptysis.
- Partial obstruction → wheeze or unresolved pneumonia.
- Complete obstruction with lung collapse → dyspnoea [1].
| Structure Involved | Symptom/Sign | Explanation |
|---|---|---|
| Bronchus (central) | Cough, haemoptysis, post-obstructive pneumonia | Tumour in airway lumen or compressing it |
| Pleura | Pleuritic chest pain, pleural effusion | Direct invasion or lymphatic obstruction |
| Chest wall / ribs | Chest wall pain | Direct invasion (Pancoast tumour at apex → shoulder/arm pain, Horner's syndrome) |
| Recurrent laryngeal nerve | Hoarseness | Left RLN loops under aortic arch — vulnerable to mediastinal tumours/LNs |
| Phrenic nerve | Elevated hemidiaphragm, dyspnoea | Paralysis of diaphragm |
| SVC | SVC obstruction syndrome (facial swelling, plethora, distended neck veins, arm oedema) | Tumour/LN compressing or invading SVC |
| Oesophagus | Dysphagia | Extrinsic compression |
| Pericardium | Pericardial effusion, tamponade | Direct invasion |
| Sympathetic chain (apex) | Horner's syndrome (ptosis, miosis, anhidrosis, enophthalmos) | Pancoast tumour |
| Brachial plexus (apex) | Arm pain, weakness, wasting (T1 distribution) | Pancoast tumour |
Additional intrathoracic spread patterns shown on the slide include [1]:
- Lymphangitis carcinomatosa involving both lungs → cough and dyspnoea.
- SVC obstruction may also cause stridor, dysphagia, and facial swelling.
- Chest wall or rib involvement may cause chest pain and swelling.
- Brachial plexus (C8–T2) and inferior cervical sympathetic ganglion involvement → shoulder/arm pain and loss of sweating on one side of the face.
Extra-thoracic manifestation [1]:
- Cachexia
- Clubbing
- Supraclavicular and cervical lymph node enlargement
- Hepatic metastasis (hepatomegaly, deranged liver function)
- Brain metastasis (seizures, change in personality, vomiting)
- Bone metastasis (pathological fractures, hypercalcaemia, bone pain)
- Adrenal metastasis (rarely cortisol insufficiency)
- Spinal cord metastasis (cord compression)
- Skin metastasis
- Choroidal metastasis (impaired visual acuity)
- Unexplained anaemia
Metastasis pattern mnemonic — "Lung Loves Bones, Brain, Liver, Adrenals"
| Syndrome | Tumour Type | Mechanism |
|---|---|---|
| SIADH → hyponatraemia | Small cell | Ectopic ADH production |
| Cushing's syndrome | Small cell | Ectopic ACTH |
| Hypercalcaemia | Squamous cell | PTHrP secretion |
| Lambert-Eaton myasthenic syndrome | Small cell | Anti-VGCC antibodies |
| Hypertrophic pulmonary osteoarthropathy (HPOA) / clubbing | Any, especially adenocarcinoma & squamous cell | Mechanism unclear; involves periosteal new bone formation |
Slide 22 broadens the visual differential beyond this core table: a systemic non-metastatic presentation can include subacute cerebellar degeneration (ataxia/clumsiness), encephalopathy, peripheral neuropathy, inflammatory myopathy/dermatomyositis, or HPOA with painful tender extremities. These syndromes may precede discovery of the primary tumour; new focal neurology must still prompt urgent exclusion of structural brain or spinal metastasis.
Past Paper 2024 SAQ Q6
A 63-year-old chronic smoker with haemoptysis, weight loss, clubbing, left supraclavicular LN, 3.5 cm lung mass, and sodium of 116 mmol/L. The most likely cause of hyponatraemia is SIADH (ectopic ADH from lung cancer, likely small cell). Investigations: paired serum and urine osmolality, urine sodium. Management: fluid restriction, treat underlying cancer, ± tolvaptan/demeclocycline [10].
Different ways of recognizing lung cancer, different clinical presentation [1]:
- Clinical symptoms and signs
- Clinical syndrome (e.g. paraneoplastic, SVC obstruction)
- Incidental findings on other medical examination (e.g. CT coronary angiogram, CT abdomen)
- Identification of at-risk population — lung cancer screening
The lecture mentions lung cancer screening with low-dose CT (LDCT) in high-risk populations. Do not use its older “≥30 pack-years” shorthand as a universal rule: programmes vary by jurisdiction. For comparison, current USPSTF criteria are annual LDCT for adults aged 50–80 with ≥20 pack-years who currently smoke or quit within 15 years, after shared decision-making [23]. Screening applies to asymptomatic people; symptoms or an abnormal radiograph require a diagnostic pathway, not screening.
Visual CXR patterns from slide 17
The four example radiographs deliberately show that lung cancer is not synonymous with a solitary round nodule. It may present as:
- a peripheral or upper-zone mass, sometimes irregular or cavitating;
- a central/hilar mass;
- segmental/lobar opacity or volume loss from bronchial obstruction (including a “non-resolving pneumonia” presentation); or
- a unilateral pleural effusion, which may conceal the primary lesion.
The pattern localises the next test but does not establish histology. CT defines the lesion and nodal/pleural anatomy; tissue should be obtained by the safest route that also provides the highest stage.
Part 3: Investigations for Suspected Lung Cancer
INVESTIGATIONS [1]:
- To confirm the diagnosis + histological subtypes
- To stage the tumour + assess fitness of patient → to select treatment modality
| Modality | Purpose |
|---|---|
| CXR | First-line; may show mass, effusion, collapse, mediastinal widening |
| CT thorax + upper abdomen | Characterise lesion, assess LN, look for liver/adrenal metastases |
| PET-CT | Excellent tumour imaging. FDG is taken up by cells in glycolysis but is trapped — increased activity in cells with high metabolic rates (tumours and inflammation) [1]. Used for staging: detects distant metastases, helps differentiate benign vs. malignant LN |
PET-CT: Why does it work?
FDG (fluorodeoxyglucose) enters cells via glucose transporters and is phosphorylated but CANNOT continue through glycolysis → it accumulates in metabolically active cells (tumours). This is why cancers "light up" on PET. False positives occur with inflammation/infection (e.g. TB, sarcoidosis). False negatives can occur with low-grade tumours (e.g. carcinoid, some adenocarcinoma in situ). [1]
How to read the slide 26 PET-CT: the fused axial image demonstrates where CT anatomy and FDG avidity overlap, while the whole-body maximum-intensity projections reveal that one thoracic lesion may coexist with multiple nodal and skeletal foci. This is why PET-CT can change a patient from a presumed local treatment pathway to systemic therapy. Physiological brain, renal/urinary and variable bowel uptake must not be mistaken for metastasis, and an avid site still needs pathological confirmation when it would change curative intent.
Additional staging and fitness assessment
The staging work-up may also include [1]:
- Blood tests: liver function, renal function, and calcium.
- Cardiac assessment and lung function assessment before treatment selection.
- CT brain and bone scan as indicated.
- Mediastinoscopy as an additional mediastinal assessment technique.
These investigations complement CT thorax/upper abdomen, PET-CT, bronchoscopy, and tissue sampling when staging the tumour and assessing fitness for treatment.
The lecture outlines multiple modalities for tissue diagnosis [1]:
| Modality | When to Use |
|---|---|
| Sputum cytology | Low sensitivity, rarely sufficient alone |
| Bronchoscopy + endobronchial biopsy | Central lesions visible in the airway |
| Bronchoscopy + transbronchial biopsy | Peripheral lesions accessible through airways |
| CP-EBUS-TBNA (Convex Probe Endobronchial Ultrasound Transbronchial Needle Aspiration) | Mediastinal/hilar lymph node sampling. Sensitivity ~90%. False negative rate ~20%. [1] |
| Radial probe EBUS with guided sheath | Peripheral lung lesions |
| Navigational bronchoscopy | Peripheral lung lesions |
| Image-guided percutaneous biopsy | Peripheral lesions not accessible by bronchoscopy |
| Pleuroscopy | Pleural-based disease, malignant pleural effusion [1] |
| Thoracentesis cytology | Pleural effusion; yield varies by tumour type and specimen processing |
| Autofluorescence imaging | Detect early endobronchial neoplasia |
The lesion-location rule in the intervention diagram (slide 27)
- Visible central endobronchial lesion: bronchoscopy with biopsy/brushings; therapeutic bronchoscopy (for example cryotherapy) may also relieve obstruction.
- Mediastinal or hilar node / mass abutting a central airway: convex-probe EBUS-TBNA.
- Peripheral pulmonary lesion: radial-probe EBUS, navigational bronchoscopy or image-guided percutaneous biopsy, selected by bronchus sign, size, location and local expertise.
- Pleural thickening/nodularity or recurrent pleural fluid: image-guided pleural biopsy or pleuroscopy; consider an IPC for recurrent symptomatic malignant effusion.
Whenever possible, biopsy the safest accessible site that confirms diagnosis and the highest suspected stage (for example, an accessible distant metastasis rather than separately sampling the lung primary).
Indications for CP-EBUS-TBNA [1]:
- Staging for lung cancer
- Sampling of mediastinal lymph nodes
- Alternative diagnosis for mediastinal lymphadenopathy (TB, sarcoidosis, lymphoma)
- Tumour mass immediately adjacent to accessible part of the airway
The nodal map on slide 29 makes the reach of convex EBUS concrete: it commonly samples upper/lower paratracheal nodes (2R/2L, 4R/4L), subcarinal (7) and hilar/interlobar stations (10/11). Not every mediastinal station is reachable from the airway (notably aortopulmonary-window/para-aortic stations 5/6), so negative EBUS or inaccessible suspicious nodes may require EUS-based or surgical staging depending on pre-test probability and whether the result changes treatment.
Endobronchial biopsy showed adenocarcinoma [1]:
- CK7 positive
- CK20 negative
- TTF-1 positive
What do these markers mean?
- CK7+/CK20−: Typical of pulmonary adenocarcinoma (CK20+ would suggest GI origin)
- TTF-1 (Thyroid Transcription Factor-1): Expressed in lung and thyroid. In the right morphology and clinical/radiological context, TTF-1 positivity supports primary lung adenocarcinoma, but no single immunostain “confirms” origin in isolation.
Liquid biopsy – to supplement when tissue biopsy is difficult or impossible [1]
| Liquid Biopsy | Tissue Biopsy |
|---|---|
| Relatively non-invasive | Mostly invasive |
| Allows serial monitoring | At diagnosis ± re-biopsy on progression/drug failure |
| Examples: CTC, ctDNA, miRNA, tumour-derived exosomes, oncogenic proteins | Primary tumour histology, metastatic site biopsy |
| Lack of standardised techniques | Well-established/gold-standard |
| Variable sensitivity (tumour cell material leakage dependent) | Sampling representativeness of small biopsy |
Clinical applications of circulating biomarkers [1]:
- For diagnosis
- To guide targeted therapy selection
- To monitor disease progress / treatment response
- To identify new targets
- Early detection of disease recurrence
- For prognostication
Gold-standard for diagnosis is still lung cancer tissue for histological diagnosis [1]
Key point: Plasma ctDNA is validated mainly for molecular genotyping and resistance assessment, not for replacing histological diagnosis. A positive actionable result can guide treatment, but a negative plasma test may simply reflect low tumour shedding and should usually prompt tissue testing if feasible. The lecture's emphasis on T790M reflects the era when first-/second-generation EGFR TKIs were routinely first line; after first-line osimertinib, resistance is more heterogeneous and requires contemporary broad molecular assessment rather than a T790M-only pathway [20].
The lecture uses the 8th-edition TNM system (2018) [1]. Since 1 January 2025, lung-cancer staging has transitioned to the 9th edition. The T categories remain unchanged, while N2 is divided into N2a (single ipsilateral mediastinal/subcarinal station) and N2b (multiple N2 stations), and M1c into M1c1 (multiple metastases in one extrathoracic organ system) and M1c2 (multiple organ systems) [25]. Use the current edition for formal staging.
| Component | What It Assesses |
|---|---|
| T — Tumour | Size and local invasion |
| N — Nodes | Regional hilar/mediastinal and low cervical/supraclavicular nodes; side and number of involved stations matter |
| M — Metastasis | Distant spread |
| Stage | Broad extent | Treatment principle |
|---|---|---|
| I | Early/localised disease | Surgery if operable; curative-intent stereotactic radiotherapy is an option when surgery is unsuitable |
| II | Early/localised disease | Usually multimodal, commonly resection plus peri-operative systemic therapy when operable |
| III | Locally advanced, heterogeneous | Multidisciplinary assessment: selected IIIA disease may be resectable; unresectable disease commonly receives definitive concurrent chemoradiation followed by consolidation systemic therapy when eligible |
| IV | Metastatic disease | Biomarker-directed targeted therapy, immunotherapy and/or chemotherapy; local treatment may still be used for symptom control or selected oligometastatic disease |
Historical slide shorthand [1]: “I–II surgery; III chemoradiation; IV chemotherapy.” It is a useful first-pass map, not a current prescribing algorithm.
Why does operability matter? It is a joint anatomical and physiological decision, not a stage label alone. Selected stage III tumours can enter a surgical multimodality pathway, and medically inoperable early disease may still receive curative radiation. Current NCI guidance likewise separates surgically resectable disease (generally I, II and selected III), locally/regionally advanced disease, and distant metastatic disease [20].
Part 5: Treatment of Lung Cancer
Treatment for lung cancer [1]:
| NSCLC | SCLC | |
|---|---|---|
| Early stage | Resection | — |
| Locally advanced | Chemo ± RT ± resection | Limited stage: Chemo ± RT |
| Advanced | Chemotherapy or targeted therapy or immunotherapy | Extensive stage: Chemo |
| Relapse | Tests for targets → further options | Tests for targets |
This flowchart captures the treatment domains, but the exact sequence now depends on resectability, performance status, histology, PD-L1, brain involvement, broad molecular testing and prior therapy. Discuss cases in a thoracic multidisciplinary team rather than inferring treatment from stage alone [20].
Cyclical combination chemotherapy [1]: A platinum drug (e.g. cisplatin or carboplatin) + a newer generation cytotoxic drug (e.g. pemetrexed, taxol, gemcitabine) Response rate about 30–40% Note side effects especially myelosuppression
Workup for lung cancer systemic treatment [1]:
- Check hepatitis B carrier status — if HBV carrier, cover with antiviral prophylaxis (e.g. entecavir) throughout chemotherapy
- Pre-medications for some regimens: e.g. Vitamin B12 and folic acid supplementation before pemetrexed chemotherapy
Why HBV status matters: Chemotherapy-induced immunosuppression can reactivate dormant hepatitis B, causing fulminant hepatitis. This is extremely high-yield in Hong Kong where HBV prevalence is high.
Exam Pearl: HBV Reactivation Prevention
ALWAYS check HBsAg (and anti-HBc) before starting cytotoxic chemotherapy or immunosuppression. If HBsAg positive, start antiviral prophylaxis (entecavir preferred) BEFORE chemotherapy and continue throughout + 6–12 months after. [1]
5.4 Molecular Targeted Therapy
Molecular Targeted Therapy — Indications: As primary treatment for tumour with oncogenic molecular targets [1]
Biomarkers: Sensitising EGFR mutations [1]:
- 15-nucleotide deletion in exon 19 (del19)
- L858R or L861Q in exon 21
Resistant mutation: T790M in exon 20
(Mutations detectable in tumours or plasma DNA)
Clinical indications [1]:
- The slide's earlier sequence was sensitising EGFR mutation → gefitinib/erlotinib/afatinib; acquired T790M → osimertinib.
- In current practice, osimertinib-based therapy is commonly used up front for classical sensitising mutations, so progression should trigger broad resistance assessment rather than assuming T790M [20].
Common adverse effects from EGFR-TKI [1]:
- Skin rash (acneiform)
- Stomatitis/mucositis (WHO Grade III = can only tolerate fluid diet)
- Paronychia with ingrown toenail
- Diarrhoea
- Interstitial lung disease (rare but serious)
Biomarkers: ALK immunohistochemical staining or ALK FISH [1]
The slide associates ALK-positive NSCLC particularly with adenocarcinoma, never or light smokers, and a median age of about 50 years; it reports no sex difference [1].
Clinical indications: ALK re-arranged or IHC +ve tumour
- Historical slide sequence: crizotinib first line, then ceritinib/alectinib/brigatinib/lorlatinib. Modern CNS-active ALK inhibitors such as alectinib, brigatinib or lorlatinib have displaced crizotinib in many first-line pathways; the choice and later sequencing depend on prior drug, CNS disease and resistance findings [20].
The lecture slide on advanced NSCLC with actionable mutations [1] lists:
| Target | Drug(s) |
|---|---|
| EGFR mutation | Osimertinib (preferred), erlotinib, afatinib, gefitinib, dacomitinib |
| ALK translocation | Alectinib (preferred), brigatinib, ceritinib, lorlatinib, crizotinib |
| ROS1 rearrangement | Crizotinib or entrectinib |
| BRAF V600E mutation | Dabrafenib + trametinib |
| NTRK positive | Entrectinib or larotrectinib |
| RET positive | Selpercatinib or pralsetinib |
| METex14 positive | Capmatinib or tepotinib |
Current correction: the slide 43 panel is a 2023 snapshot, not an exhaustive 2026 list. Broad testing may also identify KRAS G12C and ERBB2/HER2 alterations, and the available drugs now include agents not shown on the slide. Use a current local molecular-oncology pathway rather than memorising one static drug chart [20].
PD-1/PD-L1 therapy [1]: Biomarker: PDL1 immunohistochemical staining intensity — Tumour Proportional Score (TPS)
- Higher PD-L1 expression (often using TPS ≥50% as a clinically important threshold) is associated with greater likelihood of response to some PD-1/PD-L1 regimens, but it is not a perfect binary test.
Why immunotherapy works: PD-L1 on tumour cells or immune cells can engage PD-1 on T cells, sending an inhibitory signal. Blocking this interaction “releases the brakes.” Be precise with drug class: pembrolizumab and nivolumab target PD-1, whereas atezolizumab targets PD-L1.
Current correction to slide 49: PD-L1 remains a treatment-selection biomarker; it is not accurate to teach that testing is simply unnecessary after first line. In advanced NSCLC without an actionable driver, PD-L1, histology, performance status and comorbidity help select checkpoint-inhibitor monotherapy versus combination immunotherapy and/or chemotherapy. When a targetable oncogenic driver is present, matched targeted therapy is generally prioritised [20].
Immune-related adverse events: the missing meaning of slide 50
The bar chart is not just a toxicity list: checkpoint blockade can inflame almost any organ, sometimes during or after treatment. Recognise the organ-pattern red flags [21]:
| Organ | Typical clue |
|---|---|
| Lung | New cough, hypoxia or dyspnoea → consider pneumonitis |
| Gut | Persistent diarrhoea/abdominal pain → colitis |
| Liver | Asymptomatic transaminase rise or hepatitis |
| Endocrine | Hypo-/hyperthyroidism, hypophysitis, adrenal insufficiency or new type 1 diabetes |
| Skin | Rash/pruritus; occasionally severe skin reactions |
| Less common but dangerous | Myocarditis, nephritis, myositis or neurological toxicity |
New symptoms should be reported promptly. Management is grade- and organ-specific and may require holding immunotherapy and giving corticosteroids or other immunosuppression; do not treat presumed infection and miss an immune toxicity, or give immunosuppression without evaluating infection where relevant [21].
| Stage | Treatment |
|---|---|
| Limited stage | Chemo ± RT |
| Extensive stage | Chemo |
SCLC is usually treated systemically, with thoracic radiotherapy incorporated for limited-stage disease and immunotherapy now used in relevant modern regimens. “Never surgery” is too absolute: surgery has a limited, non-routine role only in a carefully staged minority with very early disease, followed by systemic therapy [24]. SCLC is often initially treatment-sensitive but has a high relapse risk.
Supportive management shown in the lecture includes [1]:
- Hospice care and psychosocial support.
- Analgesics and other symptomatic treatment, including cough suppression.
- Thoracentesis and pleurodesis for symptom relief from recurrent pleural fluid.
Summary [1]:
- Variable clinical presentation of lung cancer, from asymptomatic to frank systemic disturbance or clinical syndromes
- Different diagnostic methods to suit individual presentation
- The aims of diagnostic investigation should be:
- Distinction between benign and malignant lesion
- To obtain tissue diagnosis, especially for at-risk population
- To work up for staging with diagnosis of lung cancer and to evaluate for metastasis
- Functional assessment for patients in preparation for treatment modalities
High Yield Summary
-
Pleural Effusion
- Apply Light's criteria (protein ratio > 0.5, LDH ratio > 0.6, fluid LDH > 2/3 ULN serum LDH) → exudate.
- In a chronic smoker: think malignancy.
- Lymphocyte-predominant = chronic process (malignancy, TB).
- Send 25–50 mL for cytology and cell block; yield varies by tumour type.
- If non-diagnostic, choose the next biopsy by the imaging target: pleura → image-guided biopsy/pleuroscopy; mediastinal node → EBUS; central lesion → bronchoscopy.
- A unilateral effusion requires investigation, not automatic chest-drain insertion.
-
Lung Cancer
- NSCLC = 85%.
- Adenocarcinoma is the most common subtype, especially in HK women (often non-smokers with EGFR mutations).
- CK7+/CK20−/TTF-1+ supports primary lung adenocarcinoma in the right morphological and clinical context.
- Resectability and fitness—not stage alone—determine local therapy; selected stage III disease may be resectable and medically inoperable early disease may receive curative radiotherapy.
- Advanced disease: broad molecular testing and PD-L1 guide targeted therapy, immunotherapy and/or chemotherapy.
- Always check HBV status before chemotherapy.
- Liquid biopsy supplements tissue biopsy for molecular targets.
-
Key Exam Discriminators
- Stony dull = effusion (not consolidation). Decreased VR/VF = effusion; Increased VR/VF = consolidation. Light's criteria overdiagnose exudates in diuretic patients. PET false positive in infection/inflammation.
Active Recall - Pleural Effusion and Lung Cancer
[1] Lecture slides: GC 077. Pleural effusion in a chronic smoker.pdf (all pages) [2] Senior notes: Maksim Medicine Notes.pdf (p292) [3] Senior notes: Ryan Ho Fundamentals.pdf (p228) [4] Senior notes: Block A - Renal Replacement Therapies.pdf (p17) [5] Senior notes: Gen Clerk Anaes + Microbiology Summary.pdf (p33) [6] Senior notes: MBBS Final MB (Medicine) (Felix PY Lai).pdf (p274) [7] Senior notes: MBBS Final MB (Surgery) (Felix PY Lai).pdf (p468) [8] Lecture slides: Respiratory Examination for CFB_James Ho_2024.pdf (p52) [9] Past papers: 2024 Fourth Summative MCQ.pdf (p37, EMQ Q1-4) [10] Past papers: 2024 Fourth Summative SAQ.pdf (p7, Q6) [18] British Thoracic Society. British Thoracic Society Guideline for pleural disease. Thorax. 2023;78(Suppl 3):s1–s42. https://thorax.bmj.com/content/78/Suppl_3/s1 [19] British Thoracic Society. British Thoracic Society Clinical Statement on pleural procedures. Thorax. 2023;78(Suppl 3):s43–s68. https://thorax.bmj.com/content/78/Suppl_3/s43 [20] National Cancer Institute. Non-Small Cell Lung Cancer Treatment (PDQ®)—Health Professional Version. Updated 2025. https://www.cancer.gov/types/lung/hp/non-small-cell-lung-treatment-pdq [21] National Cancer Institute. Immune Checkpoint Inhibitors. https://www.cancer.gov/about-cancer/treatment/types/immunotherapy/checkpoint-inhibitors [22] Merck Manual Professional Edition. Pleural Effusion. Revised 2025. https://www.merckmanuals.com/professional/pulmonary-disorders/mediastinal-and-pleural-disorders/pleural-effusion [23] US Preventive Services Task Force. Final Recommendation Statement: Lung Cancer Screening. 2021. https://www.uspreventiveservicestaskforce.org/uspstf/document/RecommendationStatementFinal/lung-cancer-screening [24] National Cancer Institute. Small Cell Lung Cancer Treatment (PDQ®)—Health Professional Version. Updated 2025. https://www.cancer.gov/types/lung/hp/small-cell-lung-treatment-pdq [25] Rami-Porta R, et al. IASLC Lung Cancer Staging Project: Proposals for Revision of TNM Stage Groups in the Ninth Edition. J Thorac Oncol. 2024;19(7):1007–1027. https://pubmed.ncbi.nlm.nih.gov/38447919/
GC076 Pallor: Diagnosis Of Anaemia; Nutritional Anaemia; Anaemia Of Systemic Diseases
Pallor indicating anaemia is systematically diagnosed by evaluating hemoglobin levels and red cell indices to distinguish nutritional deficiencies (iron, B12, folate) from anaemia secondary to chronic systemic diseases such as infections, renal failure, or malignancies.
GC078 Polyuria And Polydipsia Glucose Metabolism, Diabetes Mellitus, Diabetic Ketoacidosis
Polyuria and polydipsia in the context of disordered glucose metabolism arise from osmotic diuresis due to hyperglycemia, as seen in diabetes mellitus, which can progress to diabetic ketoacidosis when severe insulin deficiency leads to uncontrolled lipolysis, ketonemia, and metabolic acidosis.