Resectable Anal Melanoma Detected by Rectal Retroflexion

Abstract

A 65-year-old African American woman with end-stage renal failure on hemodialysis presented for asymptomatic screening colonoscopy as part of routine evaluation for kidney transplantation. In addition to 3 small (<10-mm) adenomas, rectal retroflexion demonstrated a 1-cm localized area of melanin below the dentate line in the left posterior anus (Figure A, circle). Given the concern for melanoma, the patient was referred to colorectal surgery and underwent an excisional biopsy, which confirmed anal mucosal malignant melanoma characterized by nests in the submucosa (Figure B) and strong reactivity to Melan-A by immunohistochemistry (Figure C), and stage I disease was confirmed (0.9-cm greatest dimension, maximal thickness 0.5 mm, clear mucosal and deep margins, no lymphovascular invasion).