Painful, bleeding fingertip papule

A 66-year-old man presented with a 3-month history of a painful and bleeding fingertip papule that had temporarily improved after silver nitrate application. Pertinent history included stage IV clear cell renal cell carcinoma (ccRCC) treated with radical nephrectomy and adjuvant ipilimumab/nivolumab. Recent imaging confirmed continued regression of metastases, and the patient was clinically doing well. Examination demonstrated a violaceous and hyperkeratotic papule. Biopsy revealed a dermally based, lobulated, eosinophilic epithelioid cell population with extravasated red blood cells. Immunohistochemistry was negative for CD31, CK7, and CK20 and positive for AE1/AE3, AMACR, PAX8, and CD10 within the epithelioid cell population.