Malignant melanoma of the rectum.

Malignant melanoma of the rectum is an extremely rare disease. It typically presents in the fifth or sixth decade of life with nonspecific complaints such as rectal bleeding or anal pain. A timely diagnosis of anal melanoma is made even more difficult by the fact that most of the lesions lack obvious pigmentation and are even histologically amelanotic. Prognosis is very poor. Anorectal malignant melanomas spread along submucosal planes and are often beyond complete resection at the time of diagnosis. We present the radiological and pathological features seen in a 43-year-old woman diagnosed with melanoma of the rectum.