A 45-year-old woman presents with velvety hyperpigmented plaques in the axillae and neck. Endoscopy reveals a gastric mass, and biopsy confirms gastric adenocarcinoma. The skin finding is most likely mediated by which mechanism?

• A Ectopic ACTH secretion
• B Paraneoplastic pemphigus
• C Anti-desmoglein autoantibodies
• D TGF-alpha and EGFR stimulation of keratinocytes ✓

Explanation

Malignant acanthosis nigricans is a paraneoplastic manifestation of gastrointestinal adenocarcinoma, most commonly gastric. It is mediated by tumor-derived TGF-alpha acting on EGFR in the skin, causing proliferation of keratinocytes and fibroblasts. Ectopic ACTH causes Cushing syndrome. Anti-desmoglein antibodies and paraneoplastic pemphigus cause blistering, not velvety hyperpigmented plaques.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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