A CASE OF ANORECTAL AMELANOTIC MALIGNANT MELANOMA

Anorectal amelanotic malignant melanoma is an extremely rare. There have been only 17 cases in the Japanese literature so far. We report a case of anorectal amelanatic malignant melanoma. A 58-year-old woman was seen at the hospital because of anal bleeding and anal pain. An elastic soft and elevated mass was palpated in the anal canal. The patient was diagnosed as the desease by histolagical examination of biopsy specimen which was stained by hematoxylin and eosin. Abdominoperitoneal resection was performed. The resected specimen showed a light grey tumor resembling Borrmann I type, sized 6.5×3.5×2.2cm just above the dentate line. The tumor stained positive for S-100 protein and HMB-45 monoclonal antibody. Adjuvant chemotherapy with dacarbazine, cisplatine, tamoxifen was done, but the patient died of cachexia seven months after the operation. To imorove the prognosis of the desease, we would emphasize the importance of preoperative diagnosis, especially our surgion's careful attitude to suspect the disease based on macroscopic findings.