A 55-year-old man with poorly-controlled diabetes develops velvety, hyperpigmented, thickened skin in the axillae and neck. He is later found to have a T2 gastric carcinoma. Which mechanism links these two entities through this dermatosis?

• A Tumour-produced TGF-alpha binding EGF receptors on keratinocytes causing acanthosis ✓
• B Insulin resistance driving EGF receptor over-stimulation from both insulin and tumour-derived EGF
• C Paraneoplastic autoantibodies against melanocyte-stimulating hormone receptor
• D Excess ectopic ACTH from the gastric tumour causing hyperpigmentation

Explanation

Malignant acanthosis nigricans (particularly gastric carcinoma-associated) is caused by tumour secretion of TGF-alpha and other EGF-receptor ligands, which stimulate keratinocyte and fibroblast proliferation, producing the velvety acanthotic plaques. In the diabetic/obese context, hyperinsulinaemia stimulates IGF-1 receptors on keratinocytes, causing the benign variant. The paraneoplastic variety tends to be more florid, rapid-onset, and involves mucosa/palms.

Reference: Neena Khanna Illustrated Synopsis of Dermatology & STD, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.