Four Cases of Rectal Melanoma

ABSTRACT

Although anal canal is the most common site for the development of malignant melanoma in the alimentary tract, it is extremely rare and melanoma can occur primarily at lower rectum. Anorectal melanoma constitutes 0.4% to 0.8% of colorectal malignancies and less than 2% of melanomas. The prognosis may depend on the extent of disease and depth of invasion. It generally seems to be very poor in spite of aggressive treatment. We have treated four patients of rectal melanomas out of 1,477 cases of all colorectal cancer between September, 1989 and January, 1997 ; a 39-year-old female with the intermittent blood-tinged stool, a 51-year-old male with hematochezia, a 59-year-old male with anal bleeding and a 65-year-old female with anal bleeding. They were treated by abdominoperineal resection with pelvic lymph node dissection and were confirmed histologically rectal melanomas.