[Colorectal melanoma: review of two distinct forms of presentation].

Malignant melanoma of the colon and rectum is an infrequent disease. Primary anorectal melanoma accounts for 0.1-4.

Carcinosarcoma of the colon: report of a rare tumor.

Carcinosarcoma is a rare tumor that shows both epithelial and stromal malignant differentiation. Most reported cases of carcinosarcoma affect the female genital tract (and are called malignant mixed müllerian tumors), but there are also some isolated reports of cases affecting the lung and the head and neck area. Carcinosarcomas only rarely affect the gastrointestinal tract, mainly the esophagus.