Malignant melanoma can occur in various anatomic locations of the human body. Apart from the skin (91.2%), possible locations include eye (5.5%) and mucosal membranes (1.3%). In 2.2% of the cases the location of the primary tumor remains unclear. We report a case of a 78 year-old female patient presenting with obstipation and itching in the perianal region. Rectal examination showed a black mass in the anal canal, histology revealed a primary mucosal melanoma. We performed a wide local excision, followed by abdominoperineal resection as the tumor was detected in a locally advanced state.