Snapshot A 56-year-old man presents with several giant dark spots that appear "dirty." He describes them as velvet-like. Scrubbing the lesions with soap and water does not remove the skin abnormality. On exam, there are hyperpigmented plaques in the axillary and neck fold region. His primary care doctor is concerned for an occult malignancy given its rapid developement. Introduction Velvety hyperpigmentation of flexural skin Pathogenesis hyperplasia of stratum spinosum of epidermis cutaneous marker of high insulin Associated conditions obesity diabetes other states of hyperinsulinemia (e.g., Cushing’s disease) medications occult malignancy gastric cancer MEN 2B Presentation Symptoms non-tender, non-itchy dirty appearance that is not removed with washing with diabetes and obesity gradual onset with malignancy rapid and sudden onset Physical exam velvet-textured, hyperpigmented plaques surface is rough, warty, or papillomatous locations axillae neck other skin folds less common Evaluation Laboratory values elevated glucose elevated insulin Screen for diabetes or malignancy if appropriate Differential Diagnosis Melasma Fungal infection Atopic dermatitis Treatment Treat underlying condition Lesions do not typically require treatment optional: topical retinoids Prognosis, Prevention, and Complications Prognosis for obesity-related plaques improve with weight loss for malignancy-related plaques resolve with successful treatment