small cell lung cancer
Summary
Small cell lung cancer (SCLC) is an aggressive neuroendocrine tumor comprising ~15% of lung cancers, strongly associated with smoking. It has rapid growth, early metastasis, and initial responsiveness to chemotherapy but poor overall prognosis with 5-year survival <10%.
Detail
Small cell lung cancer arises from neuroendocrine cells (Kulchitsky cells) in the bronchial epithelium and is characterized by small, round cells with scant cytoplasm and hyperchromatic nuclei. It's classified as a high-grade neuroendocrine carcinoma with rapid doubling time and early widespread metastasis. SCLC is strongly linked to smoking (>95% of cases) and typically presents as a central/hilar mass. The tumor frequently produces ectopic hormones leading to paraneoplastic syndromes including SIADH (hyponatremia), Cushing syndrome (ACTH), Lambert-Eaton myasthenic syndrome, and cerebellar degeneration. Staging uses limited vs. extensive disease rather than TNM. Limited disease (confined to one hemithorax) has better prognosis and may be treated with concurrent chemoradiation, while extensive disease requires systemic chemotherapy. Despite initial chemosensitivity, resistance typically develops within 6-12 months. Prophylactic cranial irradiation is considered for patients with good response to prevent brain metastases.
Sources
- Robbins and Cotran Pathologic Basis of Disease
- Harrison's Principles of Internal Medicine
- NCCN Clinical Practice Guidelines in Oncology
- First Aid for the USMLE Step 1
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