Generalized melanosis caused by melanoma of the rectum.

Only 29 cases of generalized melanosis caused by melanoma have been described in the English-language literature since the beginning of this century. This is the first reported case in which the primary site of melanoma was the mucosal surface of the rectum and melanosis was a presenting sign of the disease. Generalized melanosis carries a dismal prognosis; none of the reported patients lived beyond 1 year after the onset of pigmentation.