Lung Cancer & Thoracic Surgery

Lung cancer is the leading cause of cancer-related death worldwide and a perennial NEET PG favourite, blending oncology, radiology and surgical decision-making. This topic also sweeps in mediastinal masses, Pancoast tumour, and the thymoma–myasthenia link, so a tight grip on classification, staging and resectability is high-yield.

Classification

Lung cancer is broadly divided into Small-Cell Lung Cancer (SCLC) and Non-Small-Cell Lung Cancer (NSCLC) — the single most important division because it dictates whether the patient goes to the operating theatre or to the oncologist.

Feature	NSCLC (~85%)	SCLC (~15%)
Subtypes	Adenocarcinoma, squamous cell, large cell	Oat cell (neuroendocrine)
Location	Adeno = peripheral; Squamous = central	Central (perihilar)
Smoking link	Squamous & SCLC strongest; adeno weakest	Very strong
Behaviour	Slower, local then spread	Aggressive, early metastasis
Paraneoplastic	PTHrP (squamous → hypercalcaemia)	SIADH, ectopic ACTH, LEMS
Primary treatment	Surgery (early stage)	Chemo + radiotherapy (rarely surgery)
Marker	—	NSE, chromogranin, synaptophysin

High-yield: SCLC is treated medically (chemo-radiotherapy), almost never surgically because it has usually metastasised at presentation. NSCLC is the surgical disease. This NSCLC vs SCLC distinction is the most repeated single fact in this topic.

Adenocarcinoma is now the commonest lung cancer overall and the commonest in non-smokers and women. It is peripheral and associated with EGFR, ALK and ROS1 mutations (targets for tyrosine kinase inhibitors). Squamous cell carcinoma is central, cavitates, and is classically linked to hypercalcaemia via PTHrP and Pancoast tumour.

Etiology & Risk Factors

• Smoking — the dominant cause; risk proportional to pack-years. Squamous and small-cell have the strongest association.
• Asbestos — synergistic with smoking; also causes mesothelioma.
• Radon gas, arsenic, chromium, nickel, polycyclic aromatic hydrocarbons.
• Radiation, pulmonary fibrosis (scar carcinoma → adenocarcinoma).
• Genetic: EGFR (Asian, non-smokers, women), ALK rearrangement, KRAS (smokers).

Clinical Features

• Cough (commonest symptom), haemoptysis, dyspnoea, recurrent pneumonia in the same lobe (suggests endobronchial obstruction).
• Chest pain, weight loss, clubbing, hypertrophic pulmonary osteoarthropathy.
• Local invasion: hoarseness (recurrent laryngeal nerve), elevated hemidiaphragm (phrenic nerve), dysphagia (oesophagus), SVC obstruction.
• Superior Vena Cava Obstruction (SVCO): facial/upper limb swelling, dilated chest wall veins, plethora — most often from a right-sided central tumour or SCLC. It is an oncological emergency managed with steroids, radiotherapy/chemo, and endovascular stenting.

Pancoast (Superior Sulcus) Tumour

A tumour of the lung apex invading the structures of the thoracic inlet.

High-yield: Pancoast syndrome = shoulder/arm pain (C8–T1 brachial plexus) + Horner syndrome (ptosis, miosis, anhidrosis, enophthalmos — from sympathetic chain/stellate ganglion involvement) + hand muscle wasting + rib destruction.

• Usually NSCLC (squamous).
• Best imaging = MRI (assesses brachial plexus, vessels, vertebral invasion).
• Treatment = neoadjuvant chemo-radiotherapy followed by surgical resection (en bloc), if no T4 unresectable invasion.

Paraneoplastic Syndromes (frequently tested)

Syndrome	Mechanism	Cancer
Hypercalcaemia	PTHrP	Squamous cell
SIADH (hyponatraemia)	ADH	Small cell
Cushing	Ectopic ACTH	Small cell
Lambert-Eaton myasthenic syndrome	Anti-VGCC antibodies	Small cell
Hypertrophic pulmonary osteoarthropathy	—	Adenocarcinoma

Diagnosis & Investigations

Stepwise approach: Suspicious symptoms/CXR → Contrast CT chest + upper abdomen (extent, nodes, adrenals/liver) → Tissue diagnosis (biopsy/cytology) → PET-CT for distant mets & nodal uptake → Mediastinal nodal staging (EBUS/mediastinoscopy) → Brain MRI if neurological/SCLC → Pulmonary function tests for operative fitness → MDT decision.

• Chest X-ray: first investigation; coin lesion, hilar mass, collapse, effusion.
• CECT chest: investigation of choice for anatomical staging and resectability.
• Tissue diagnosis: bronchoscopy + biopsy/brushings (central tumours), CT-guided percutaneous transthoracic biopsy (peripheral lesions), pleural fluid cytology, sputum cytology.
• PET-CT: detects occult metastases and characterises mediastinal nodes; standard before curative surgery.
• EBUS-TBNA (endobronchial ultrasound) — minimally invasive sampling of mediastinal nodes; now often the first nodal-staging step.

Mediastinoscopy

High-yield: Mediastinoscopy is the gold standard for mediastinal lymph node staging (assessing N2/N3 disease). Cervical mediastinoscopy (suprasternal incision) samples paratracheal and subcarinal nodes (stations 2, 4, 7). The presence of contralateral (N3) mediastinal nodes generally makes the tumour unresectable.

• Chamberlain procedure (anterior mediastinotomy) samples aortopulmonary window nodes (station 5/6) — left upper lobe tumours — not reachable by cervical mediastinoscopy.

TNM Staging Essentials

Descriptor	Key cut-offs
T1	≤3 cm surrounded by lung/visceral pleura
T2	>3–5 cm, or main bronchus involvement, or visceral pleura
T3	>5–7 cm, or chest wall/phrenic nerve/parietal pericardium, separate nodule same lobe
T4	>7 cm, mediastinum, heart, great vessels, carina, diaphragm, separate nodule different ipsilateral lobe
N1	Ipsilateral peribronchial/hilar
N2	Ipsilateral mediastinal/subcarinal
N3	Contralateral mediastinal/hilar, scalene, supraclavicular
M1a	Contralateral lobe nodule, pleural/pericardial effusion
M1b/c	Distant metastasis

High-yield: N3 disease, T4 invasion of vital structures, malignant pleural effusion (M1a), and distant metastasis are markers of inoperability. Most resectable NSCLC is Stage I–II and selected IIIA.

Management — NSCLC

• Stage I–II (and selected IIIA): Surgical resection ± adjuvant chemotherapy.
• Stage IIIA (N2): multimodal — neoadjuvant chemo ± radiotherapy then surgery, or definitive chemo-radiotherapy.
• Stage IIIB/IV: non-surgical — chemotherapy, radiotherapy, targeted therapy (EGFR-TKI such as gefitinib/osimertinib; ALK inhibitors such as crizotinib/alectinib), and immunotherapy (PD-1/PD-L1 inhibitors — nivolumab, pembrolizumab).

Surgical Procedures

High-yield: Lobectomy is the standard/preferred curative operation for resectable NSCLC because it balances oncological clearance with lung preservation. Pneumonectomy is reserved for centrally-placed tumours crossing a fissure or involving the main bronchus.

Procedure	Indication	Note
Lobectomy	Localised tumour confined to one lobe	Procedure of choice
Pneumonectomy	Central tumour, crossing fissures, main bronchus	Higher mortality (~right > left)
Sleeve resection	Tumour at lobar bronchus origin	Spares lung parenchyma, avoids pneumonectomy
Wedge/segmentectomy	Small peripheral T1, poor reserve	Sub-lobar; higher recurrence
VATS lobectomy	Early stage	Minimally invasive, less morbidity

Mediastinal lymph node dissection/sampling accompanies resection for accurate staging.

Assessing Operative Fitness (PFT)

High-yield: Pre-operative FEV1 > 2 L (or >80% predicted) usually permits pneumonectomy; FEV1 > 1.5 L permits lobectomy. Predicted post-operative (ppo) FEV1 < 40% or ppo DLCO < 40% indicates high risk. A VO2 max < 10 mL/kg/min is a contraindication to major resection.

Management — SCLC

Classified by VALSG into limited stage (one hemithorax, single radiotherapy port) and extensive stage.

• Limited: concurrent chemotherapy (platinum + etoposide) + thoracic radiotherapy.
• Extensive: chemotherapy ± immunotherapy.
• Prophylactic Cranial Irradiation (PCI) is offered to responders because of the high incidence of brain metastasis.
• Surgery only in the rare very early, node-negative T1N0 SCLC.

Mediastinal Masses (commonly examined alongside)

Localising the mass to a compartment narrows the differential rapidly.

Compartment	Common masses
Anterior (the 4 T's)	Thymoma, Teratoma/germ cell, Thyroid (retrosternal), Terrible lymphoma
Middle	Lymphadenopathy, bronchogenic & pericardial cysts, vascular
Posterior	Neurogenic tumours (schwannoma, neurofibroma, neuroblastoma)

Mnemonic — anterior mediastinal masses = "4 T's": Thymoma, Teratoma (germ cell), Thyroid, Terrible lymphoma.

Mediastinal Germ Cell Tumours

• Arise from misplaced primordial germ cells; anterior mediastinum, typically young males.
• Teratoma is commonest (benign mature teratoma); seminoma is the commonest malignant pure type (radiosensitive, good prognosis).
• Non-seminomatous GCT raise AFP and β-hCG — always send these markers. (Pure seminoma → normal AFP, β-hCG may be mildly raised.)
• Associated with Klinefelter syndrome and rarely haematological malignancy.
• Treatment: seminoma — chemo/radiotherapy very responsive; NSGCT — cisplatin-based chemotherapy then resection of residual mass.

Thymoma & Myasthenia Gravis

High-yield: Thymoma is the commonest anterior mediastinal mass in adults, and 10–15% of myasthenia gravis patients have a thymoma, while ~30–50% of thymoma patients have myasthenia gravis. All MG patients need a CT chest to look for thymoma.

• Other thymoma associations: pure red cell aplasia, hypogammaglobulinaemia (Good syndrome).
• Staged by the Masaoka–Koga system (based on capsular/local invasion).
• Treatment of choice = surgical resection (thymectomy), typically via median sternotomy; adjuvant radiotherapy for invasive disease.
• Thymectomy can improve myasthenia even without thymoma (in generalised AChR-antibody-positive MG).

Solitary Pulmonary Nodule (SPN)

A round opacity ≤3 cm surrounded by lung. Features favouring benign: small, smooth, central/popcorn/laminated calcification (granuloma, hamartoma), stable >2 years. Features favouring malignant: >3 cm, spiculated/irregular, eccentric calcification, upper lobe, growth, smoker, older age. PET-CT helps; biopsy or resect suspicious lesions.

Complications

• Of disease: SVCO, Pancoast/Horner, haemoptysis, pleural effusion, paraneoplastic syndromes, metastasis (brain, bone, liver, adrenal).
• Of pneumonectomy: post-pneumonectomy bronchopleural fistula (presents with cough productive of serosanguinous fluid + falling fluid level on CXR — a feared complication), empyema, cardiac herniation, post-pneumonectomy pulmonary oedema, arrhythmia.
• Of any thoracotomy: atelectasis, pneumonia, prolonged air leak, chylothorax (thoracic duct injury), wound issues.

Key Differentials

• Pulmonary tuberculoma / granuloma (calcified SPN, endemic — major mimic in India).
• Hamartoma (popcorn calcification, fat density on CT).
• Pulmonary metastasis (cannonball lesions — think renal, choriocarcinoma, sarcoma).
• Carcinoid tumour (central, well-vascularised, may cause haemoptysis; low-grade neuroendocrine).
• Mesothelioma (asbestos, pleural-based, unilateral effusion).
• Lymphoma, sarcoidosis for mediastinal adenopathy.

Recently asked / exam angle

• Pancoast tumour features and Horner syndrome components — recurring single-best-answer.
• NSCLC vs SCLC treatment — "which is treated surgically?" (NSCLC).
• Mediastinoscopy = gold standard for mediastinal nodal staging; Chamberlain procedure for AP window nodes.
• Lobectomy is the standard curative resection; pneumonectomy indications and FEV1 cut-offs.
• Thymoma–myasthenia gravis association and need for CT chest in MG.
• Anterior mediastinal mass "4 T's" and germ cell tumour markers (AFP/β-hCG).
• Paraneoplastic matching: squamous → PTHrP/hypercalcaemia; small cell → SIADH/ACTH/LEMS.
• SVC obstruction commonest underlying malignancy (lung, especially SCLC) and stenting.
• Adenocarcinoma = commonest type, peripheral, non-smoker/women, EGFR/ALK mutations.
• Bronchopleural fistula post-pneumonectomy presentation.

Rapid revision

1. NSCLC (85%) = surgical; SCLC (15%) = chemo-radiotherapy, surgery almost never.
2. Adenocarcinoma = commonest lung cancer, peripheral, non-smokers/women, EGFR/ALK.
3. Squamous = central, cavitates, PTHrP → hypercalcaemia, Pancoast.
4. Small cell = central, SIADH, ectopic ACTH, Lambert-Eaton (anti-VGCC).
5. Pancoast triad: arm pain (C8–T1) + Horner (ptosis/miosis/anhidrosis) + hand wasting; MRI is best; neoadjuvant chemo-RT then surgery.
6. CECT chest = staging investigation of choice; PET-CT for occult mets/nodes.
7. Mediastinoscopy = gold standard mediastinal nodal staging; Chamberlain for AP-window nodes.
8. N3, T4 vital-structure invasion, malignant effusion (M1a), distant mets = inoperable.
9. Lobectomy = standard curative op; pneumonectomy needs FEV1 >2 L, lobectomy >1.5 L.
10. Anterior mediastinal mass = 4 T's (Thymoma, Teratoma, Thyroid, Terrible lymphoma).
11. Thymoma = commonest anterior mediastinal mass in adults; 30–50% have MG; treat by thymectomy.
12. Mediastinal germ cell tumour in young males; check AFP & β-hCG; seminoma radiosensitive, NSGCT chemo then resect residual.