A 50-year-old smoker develops hypercalcemia, hyponatremia, and inappropriate ADH secretion. Imaging reveals a hilar lung mass. Which histological type is most commonly responsible for ADH-mediated paraneoplastic hyponatremia?

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

Explanation

Small cell carcinoma of the lung most commonly causes SIADH (inappropriate ADH secretion) due to ectopic production of arginine vasopressin by the neuroendocrine tumor cells. Squamous cell carcinoma more typically causes hypercalcemia via PTHrP secretion. The neuroendocrine lineage of small cell tumors underlies their capacity for diverse ectopic hormone production including ADH, ACTH, and gastrin.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.