Lower Gastrointestinal Bleeding Revealing an Early-Stage Primary Anorectal Melanoma: A Case Report

Anorectal melanomas are rare and agressive malignant tumors of the anorectal region of the digestive tract. Due to their rarity and similarity to other more benign and common conditions, such as hemorrhoids, their diagnosis is often delayed, which worsens the prognosis of this aggressive disease. Histological evaluation with special immunohistochemical (IHC) staining is often essentiel to establish a confirmed diagnosis. In the localized stage, the primary treatment for this condition consists primarily of surgical resection combined with adjuvant immunotherapy.

We report the case of a 62-year-old women who presented for an etiological evaluation of mild rectal bleeding without other associated signs. Proctological examination revealed the presence of a flashy mass occupying almost the entire anal lumen, with irregular thickening of the anterior anorectal wall during rectal examination. The colonoscopy revealed a friable and ulcerated process in the lower and middle rectum, and several biopsies were performed, confirming the diagnosis of rectal melanoma. The patient was successfully treated with surgery and adjuvant immunotherapy. Discussion/ conclusion: Our case demonstrates the importance of rapid diagnosis and a multidisciplinary therapeutic approach for a better prognosis of malignant rectal melanoma.