Lung cancer is broadly classified into two main types based on size & appearance of the cancer cells under a microscope.
1. Non small cell lung cancer (NSCLC)-
- Adenocarcinoma
- Squamous cell carcinoma
- Large cell carcinoma
2. Small cell lung cancer (SCLC)-
|
Feature |
Squamous Cell Carcinoma |
Adenocarcinoma (Mnemonic: A A 1 1) |
Small Cell Carcinoma (Oat cell) |
Large Cell Carcinoma |
|
Smoking history |
Present |
Absent (m/c in non-smokers & women) |
Present |
Absent |
|
Location |
Central / hilar |
Peripheral |
Central |
Peripheral |
|
Genetics |
Loss of- • Chr 3 • Chr 17p (p53 |
Gain of function- • EGFR 1 • ALK • KRAS |
• Loss of Chr 3p (almost all) • L-MYC amplification • p53 inactivation • RB inactivation |
- |
|
Markers |
• p40 • p63 |
• MUC 1 (Mucin) • Napsin A • TTF-1
(Mnemonic: A A 1 1) |
• Synaptophysin • Chromogranin • CD57 |
– |
|
Precursor lesions |
CIS |
• AAH • AIS |
DIPNEH |
- |
|
Microscopy |
• Keratin pearls • Intercellular bridge |
• Glandular differentiation • Lepidic growth pattern • Mucin production (PYQ: INICET May 2024) |
• Small round blue cells • Salt & pepper chromatin • Azzopardi effect (Blue blood vessels) |
Poorly differentiated large cells |
|
Paraneoplastic Syndrome (PNS) |
Hypercalcemia (↑ PTHrP) |
Migratory thrombophlebitis (Trousseau phenomenon) |
Maximum PNS see. • SIADH • Cushing’s syndrome • Lambert-Eaton syndrome (Ab against VGCC) |
• Gynecomastia • Galactorrhea (↑ hCG) |
• CIS (Carcinoma in situ)
• AAH (Atypical adenomatous hyperplasia)
• AIS (Adenocarcinoma in-situ)
• DIPNEH (Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia)