[A Case Report - A Case of a Rapidly Growing Anal Canal Origin Malignant Melanoma].

An 85-year-old woman presented to her local physician in early August 2015 with a new-onset "swelling" of the anal region and was referred to our department for evaluation and treatment at the beginning of September. At our initial evaluation, the rectal examination showed a black mass lesion, approximately 3.0×1.5 cm in size, in the anal canal by November, the mass had grown to approximately 7.0×3.5 cm in size. The lesion was diagnosed as malignant melanoma by colonoscopic biopsy. Abdominal cystography computed tomography showed an area of lymphadenopathy around the rectum, but no distant metastasis was detected. The patient underwent abdominoperineal resection of the rectum in December. Her postoperative course was good, and she was discharged on the 30th postoperative day. Arecurrent lesion was detected at a recent follow-up examination(approximately 5 months post-discharge), and the patient has been scheduled for immunotherapy. Malignant melanoma of the anal canal has a poor prognosis, and no standard therapy has been established. This report includes a brief review of current literature about the disease.