Transperineal abdominoperineal resection for anorectal melanoma: A case report

•Anorectal malignant melanoma is rare and prone to metastasis.•An anorectal melanoma was resected via transperineal abdominoperineal resection (TpAPR).•The patient remained disease-free until the 24-month follow-up.•TpAPR/total mesorectal excision (TME) for anorectal melanoma appears to be a feasible approach. Anorectal melanoma is a rare type of cancer characterized by frequent metastasis. We report our experience with a case of anorectal melanoma resected via transperineal abdominoperineal resection and total mesorectal excision. A 77-year-old woman visited our hospital with the complaint of melena. Colonoscopic examination revealed a black type 1 tumor measuring 5 mm in size on the dentate line of the anal canal circumference. Tumor biopsy revealed malignant melanoma, and positron emission tomography-computed tomography showed tracer accumulation within the mass but not at other sites. We performed a two-stage abdominoperineal resection surgery with lymphadenectomy via transperineal abdominoperineal resection, and pathological diagnosis indicated submucosal tumor depth. The patient was diagnosed with T2 N0 M0 stage I malignant melanoma and was followed on an outpatient basis. A 24-month follow-up computed tomography revealed multiple liver metastases. Anorectal melanoma is associated with a very poor prognosis because of its association with early lymph node metastasis and distant metastasis. The tumor may spread beyond the main lesion and involve the surrounding mucosa and draining lymph nodes. Transperineal abdominoperineal resection is a minimally invasive procedure that can be used to achieve curative tumor resection with lymphadenectomy. Transperineal abdominoperineal resection appears to be a feasible approach for the treatment of anorectal melanoma.