[Malignant anorectal melanoma. Apropos 1 case].

A case of malignant anorectal melanoma is reported, which was treated by anorectal-sigmoid amputation, operation which did not prevent the occurrence, after 6 months, of metastases in the inguinal lymph nodes. On the basis of the reported case, the main etiological, histogenetic, prognostic and therapeutic aspects of these rare tumours are discussed.