A Case of Anorectal Malignant Melanoma Responding to Chemotherapy in Early Postresection Recurrence

Abstract

Malignant anorectal–origin melanoma is relatively rare and its prognosis oppressive. We report a case in which chemotherapy was effective in early postoperative anorectal malignant melanoma metastasis/redevelopment. A 77–year–old woman noting blood during bowel movements in August 2007 underwent transanal resection elsewhere under a diagnosis of anal polyp. Histopathologically, moderately to poorly differentiated adenocarcinoma had invaded to the submucosa. Postoperative FDG positron emission tomography (PET) showed abnormal pararectal lymph node accumulation, but definite diagnosis was not possible based on colonoscopic biopsy after reexamining previous pathological samples. Based on a diagnosis of malignant melanoma, we conducted abdominoperineal rected resection in November 2007. Pathological diagnosis indicated malignant rectal melanoma with SM, N₂ (35/62), ly₃, and v₀. Despite a favorable postoperative course and discharge on hospitalization day 17, she was diagnosed with metastasis/redevelopment of melanoma in the early postoperative phase. Chemotherapy proved effective, and she is currently continuing it.