A 60-year-old male smoker presents with a central hilar mass on CXR with post-obstructive atelectasis. Bronchoscopic biopsy shows malignant cells with nuclear molding, scant cytoplasm, and positive immunostaining for synaptophysin and CD56. What is the most likely diagnosis?

• A Squamous cell carcinoma
• B Large cell carcinoma
• C Adenocarcinoma
• D Small cell carcinoma ✓

Explanation

Small cell lung carcinoma (SCLC) is a high-grade neuroendocrine tumor strongly associated with smoking, typically presenting as a central hilar or perihilar mass. The tumor cells are small with scant cytoplasm, hyperchromatic nuclei showing characteristic nuclear molding ('oat cells'), and express neuroendocrine markers including synaptophysin, chromogranin, and CD56. SCLC has the highest association with paraneoplastic syndromes (SIADH, Cushing, Eaton-Lambert) among lung cancers.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

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Written and medically reviewed by the StethoPrep medical team.