A rare case of recurrent primary anorectal melanoma emphasizing the importance of postoperative follow-ups

Background Primary anorectal melanoma can be a rare differential diagnosis of anorectal mass. Due to the low case number reported in the literature, physicians are not aware of this aggressive disease. Although no consensus exists, wide local excision and abdominoperineal resection are considered the mainstay therapy. Case presentation An 85-year-old female patient presented with fecal incontinence 5 years after local resection of a primary anorectal melanoma. In the rectoscopy, a tumor proximal to the dentate line was identified and later confirmed as a recurrent primary anorectal melanoma. There were no signs of locoregional or distant metastasis on the MRI and PET/CT. She underwent another wide local excision and regained fecal continence postoperatively. Conclusions Primary anorectal melanoma should belong to the differential diagnosis of anorectal mass. If technically feasible, wide local excision represents a less invasive treatment than abdominoperineal resection, retaining the anal sphincter and patient's quality of life. Even though wide local excision has a higher recurrence rate than abdominoperineal resection, there is no difference in survival between the two procedures. This is only under the premise that patients are followed-up regularly after wide local excision so that recurrence can be spotted early on and locally excised.