A 65-year-old heavy smoker with a central lung mass on imaging undergoes bronchoscopy with biopsy showing large polygonal cells with abundant pale cytoplasm, prominent intercellular bridges, and keratin pearls. This squamous cell carcinoma most commonly causes which paraneoplastic syndrome?

• A Syndrome of inappropriate ADH secretion (SIADH)
• B Cushing syndrome via ectopic ACTH
• C Lambert-Eaton myasthenic syndrome
• D Hypercalcaemia of malignancy via PTHrP secretion ✓

Explanation

Squamous cell carcinoma of the lung is the most common cause of humoral hypercalcaemia of malignancy via PTHrP (parathyroid hormone-related protein) secretion, which activates PTH receptors and causes bone resorption and hypercalcaemia. SIADH and ectopic ACTH are associated with small cell lung carcinoma; Lambert-Eaton syndrome is also associated with small cell carcinoma (anti-VGCC antibodies).

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.