Anorectal melanoma is a rare subtype of melanoma affecting the anorectal region. Anorectal melanoma is reported as arising in all 3 zones of the anal canal (upper zone with columnar epithelium, transitional zone at the pectinate line, and lower zone with squamous epithelium), but overwhelmingly so on the transitional zone. Anorectal melanoma affects older patients and has a slight predilection for females and people of Northern European descent. The melanoma may be pigmented or nonpigmented.

Anorectal melanoma is a diagnostic challenge. Patients may present with varying nonspecific symptoms, including hematochezia, rectal pain, constipation / diarrhea, anal discharge, tenesmus, anemia, and weight loss. A prolapsing mass may be a presenting sign in a minority of patients. Prognosis is very poor due to delayed presentation and diagnostic difficulty. Disease-related morbidity and mortality are high, with a median survival of 15.5 months after diagnosis.