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🌬️ Lung cancer is the leading cause of cancer death worldwide. It is divided into Small Cell Lung Cancer (SCLC) (~20%) and Non-Small Cell Lung Cancer (NSCLC) (~80%). 🚬 90% of cases are linked to smoking, though occupational and genetic factors also play a role. 📈 >40,000 new cases are diagnosed in the UK annually, with rising incidence in women due to changing smoking trends.

🧬 Aetiology & Risk Factors

🚬 Smoking – the dominant risk factor, esp. for squamous cell and SCLC.
🏭 Occupational exposures: asbestos, radon gas, silica, nickel, chromium, arsenic.
🌡️ Underlying lung disease: COPD, pulmonary fibrosis, TB scars.
🧪 Genetic mutations: EGFR, ALK, KRAS, PD-L1 expression influence prognosis and therapy.

🔬 Histological Types

Small Cell Lung Cancer (SCLC) (~20–30%)
- Central, aggressive, rapid doubling time.
- Almost always metastatic at diagnosis.
- ⚠️ Strongly linked to paraneoplastic syndromes.
- 💊 Chemo ± radiotherapy mainstay; surgery rarely used.
Non-Small Cell Lung Cancer (NSCLC) (~80%), subtypes:
- Adenocarcinoma 🌿 – peripheral, most common subtype, better prognosis, seen in smokers & non-smokers.
- Squamous Cell Carcinoma 🔥 – central, strongly smoking-related, often cavitates, can secrete PTHrP → hypercalcaemia.
- Large Cell Carcinoma ⚡ – peripheral, poorly differentiated, aggressive.

🩺 Clinical Presentation

Local: cough, haemoptysis, chest pain, recurrent pneumonia, dyspnoea.
Regional: hoarseness (recurrent laryngeal nerve), SVCO, Pancoast tumour (Horner’s, shoulder pain, arm weakness).
Systemic: weight loss, fatigue, anorexia.
Paraneoplastic: hormonal or immune-mediated effects (see below).

🧪 Paraneoplastic Syndromes in Lung Cancer


Syndrome	Mechanism	Associated Type	Clinical Features
SIADH 💧	ADH secretion	SCLC	Hyponatraemia → confusion, seizures, coma
Cushing’s Syndrome 🌙	ACTH secretion	SCLC	Hypertension, central obesity, skin changes, muscle weakness
Hypercalcaemia ☀️	PTHrP secretion	Squamous NSCLC	Thirst, polyuria, constipation, confusion
Lambert-Eaton Myasthenic Syndrome ⚡	Autoantibodies against presynaptic Ca²⁺ channels	SCLC	Proximal muscle weakness, autonomic dysfunction, improves with activity
Hypertrophic Pulmonary Osteoarthropathy (HPOA) 🦴	Unknown (possibly VEGF/PDGF)	Adenocarcinoma	Clubbing, painful periostitis

🔎 Investigations

🩸 Bloods: FBC, U&E, calcium, LFTs.
📷 Imaging: CXR → CT chest/abdomen ± PET-CT for staging.
🔬 Tissue: bronchoscopy, EBUS, CT-guided biopsy, mediastinoscopy.
🧪 Molecular: EGFR, ALK, PD-L1 testing for targeted therapy planning.

📊 Staging (NSCLC – Simplified)

Stage I: Local tumour, no nodal disease.
Stage II: Ipsilateral hilar nodes.
Stage III: Mediastinal or contralateral nodes/local invasion.
Stage IV: Distant metastases or malignant effusion.

🛠️ Management

NSCLC:
- Stage I–IIIA → Surgery (lobectomy preferred) ± adjuvant chemo/RT.
- Stage IIIB–IV → Chemo, immunotherapy, targeted therapy ± palliative RT.
SCLC: Almost always systemic at diagnosis → chemo ± radiotherapy; prophylactic cranial irradiation in responders.
💡 All patients discussed in MDT (oncology, thoracic surgery, pulmonology, radiology, palliative care).

⚖️ Comparison Table – SCLC vs NSCLC

Feature	SCLC	NSCLC
Prevalence	~20%	~80%
Growth	Very rapid, early spread	Slower, variable
Location	Central	Central (squamous) or peripheral (adeno)
Paraneoplastic	Very common (SIADH, ACTH, LEMS)	Less common (PTHrP → hypercalcaemia, HPOA)
Prognosis	Poor, median survival months without treatment	Stage- and subtype-dependent, potentially curable
Treatment	Chemo ± RT, no surgery	Surgery (if early) ± chemo/RT/targeted therapy

🚀 Newer Advances

📈 Screening: Low-dose CT in high-risk smokers (early detection).
🎯 Targeted therapy: EGFR inhibitors (gefitinib, osimertinib), ALK inhibitors (crizotinib), ROS1 inhibitors.
🛡️ Immunotherapy: Checkpoint inhibitors (pembrolizumab, nivolumab) for advanced NSCLC with PD-L1 positivity.

📚 Exam Pearls

🚬 90% of lung cancers in smokers/ex-smokers.
⚠️ SCLC → paraneoplastic syndromes (SIADH, Cushing’s, LEMS).
🌿 Adenocarcinoma = peripheral; 🔥 Squamous = central, may cavitate.
🩺 NSCLC Stage I–IIIA → surgery mainstay; Stage IV → systemic therapy only.
👩‍⚕️ MDT discussion is essential before definitive treatment.

Cases — Lung Cancer

Case 1 — Central squamous cell carcinoma 🚬: A 67-year-old man with a 50-pack-year smoking history presents with cough, haemoptysis, and weight loss. Exam: clubbing, enlarged cervical lymph nodes. CXR: hilar mass. Biopsy: keratin pearls. Diagnosis: central squamous cell carcinoma. Managed with surgical resection if operable, plus chemo-radiotherapy.
Case 2 — Small cell lung cancer (SCLC) ⚡: A 62-year-old man presents with cough, facial swelling, and shortness of breath. Exam: raised JVP, facial plethora, dilated chest wall veins (SVC obstruction). Biopsy: small blue cells, neuroendocrine markers. Diagnosis: small cell lung cancer with superior vena cava obstruction. Managed with urgent chemo-radiotherapy; not usually surgical.
Case 3 — Adenocarcinoma (peripheral) 🌿: A 58-year-old non-smoking woman presents with persistent cough and pleuritic chest pain. CXR: peripheral mass in right lower lobe. Biopsy: adenocarcinoma. Diagnosis: peripheral adenocarcinoma of the lung. Managed with lobectomy + adjuvant chemotherapy.
Case 4 — Paraneoplastic syndrome 🔬: A 55-year-old man presents with confusion, nausea, and muscle cramps. Bloods: Na⁺ 118 mmol/L. Exam: euvolaemic, no oedema. CXR: left hilar mass. Biopsy: small cell lung carcinoma. Diagnosis: SCLC with SIADH (paraneoplastic hyponatraemia). Managed with fluid restriction, chemotherapy, and tolvaptan if resistant.
Case 5 — Pancoast tumour (apical) 💪: A 60-year-old man presents with shoulder pain radiating down his arm, hand muscle wasting, and ptosis/miosis on the left side. CXR: apical lung mass. MRI: invasion of brachial plexus. Diagnosis: Pancoast tumour (likely NSCLC) with Horner’s syndrome. Managed with combined chemo-radiotherapy and surgical resection if feasible.

Teaching Point 🩺: Lung cancer types: - NSCLC: squamous (central, smoking), adenocarcinoma (peripheral, more in non-smokers), large-cell. - SCLC: aggressive, central, early mets, paraneoplastic syndromes. Red flags: haemoptysis, persistent cough, unexplained weight loss, clubbing, paraneoplastic features. Investigations: CXR, CT chest, bronchoscopy/biopsy, staging (TNM). Management: NSCLC → surgery ± chemo; SCLC → chemo-radiotherapy, usually not surgical.

PLEASE NOTE LEGAL ADVICE: The contents are under continuing development and improvements and may contain errors of omission or fact. Feedback vital and always welcome at drokane at gmail.com. This is not to be used for the assessment, diagnosis or management of patients. It should not be regarded as medical advice. It is only for educational purposes. Please adhere to your local protocols. If you are unwell please seek healthcare advice from your doctor. This does not replace senior or specialist advice. If you do not accept this then please do not use the website. If you need medical advice, please consult a doctor or other appropriate medical professional. If you are a medical professional and you need advice then speak to your senior or colleagues.

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