Anal canal melanoma-a rare entity: A case report and review of literature

Abstract

Anorectal mucosal melanoma is one of the rarest neoplasm and accounts for approximately 0.05 percent of all colorectal malignancies and 1 percent of all anal canal cancers. Patients typically present with bleeding, a mass, anorectal pain, or a change in bowel habits. Management includes surgical resection depending upon the site along with adjuvant chemotherapy, radiotherapy and immunotherapy. 48 years old gentleman who presented with 6-month-old history of bleeding per rectum, pain and tenesmus. On digital rectal examination, a semi-circular polypoidal growth was present posteriorly 2 cm from anal verge with cranio-caudal extent of 5 cm. Biopsy was suggestive of malignant melanoma. MRI pelvis revealed asymmetric circumferential thickening of 30 mm for length of 3.8 cm located 3.4 cm from anal verge with enlarged mesorectal and extra-mesorectal lymph nodes. Patient was planned for abdomino-perineal resection. Surgery and post-operative period were uneventful. Final histopathology revealed polypoidal tan-brown, partly ulcerated growth of 4 x 2.5 x 2 cm on cut-section. These findings were consistent with malignant melanoma. All 15 lymph nodes dissected were free from tumor deposits.