Primary anorectal melanoma mimicking polyp in a scleroderma patient: a case report

Primary anorectal melanoma is an extremely rare malignancy of the gastrointestinal tract with a very poor prognosis. Due to the late presentation, most patients with primary anorectal melanoma are diagnosed at advanced stages. Scleroderma is an autoimmune disease characterized by fibrosis of the skin and visceral organs. There is an increased risk of developing cancer in scleroderma patients.

A 57-year-old Syrian female diagnosed with localized scleroderma complained of a sensation of a mass in her anal area. She was diagnosed with primary rectal melanoma and was put on neoadjuvant radiotherapy. Following the radiotherapy, the endoscopy revealed several black lesions in her anal canal, and thus abdominoperineal resection was conducted.

Malignant melanoma can occur in unsuspected locations such as the anal canal. Novel therapies like anti-CTLA4 drugs have proven efficient in controlling the disease. The lack of data in the literature on this malignancy and the absence of guidelines make it challenging for an optimal approach.