What are the risk factors for lung carcinoma ? Describe the morphological features of three major histological types of lung carcinoma.
Risk Factors for Lung Carcinoma:
The most significant risk factor is tobacco smoking (active and passive), responsible for 85–90% of cases. Other important contributors include radon gas, asbestos, heavy metals such as arsenic and chromium, air pollution (particulate matter), ionizing radiation, and a family history of lung cancer. Pre-existing lung diseases like pulmonary fibrosis or COPD, genetic predisposition, and certain occupational exposures (mining, construction, chemical industries) further elevate risk.
Morphological Features of Major Histological Types:
Adenocarcinoma: Most common, often in non-smokers; arises peripherally with glandular differentiation, mucin production, forming acini, tubules, or papillae.
Squamous Cell Carcinoma: Centrally located, strongly smoking-associated; shows keratin pearls, intercellular bridges, and polygonal cells with dense cytoplasm.
Small Cell Lung Carcinoma (SCLC): Highly aggressive, smoking-related; small cells with scant cytoplasm, “salt and pepper” chromatin, high mitotic activity, and widespread necrosis, originating from neuroendocrine cells.
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