Primary Anorectal Melanoma: Report of Two Cases and Literature Review from the Radiation Oncology Department of Mohammed VI University Hospital, Marrakech

Primary anorectal melanoma is an extremely rare and aggressive malignancy, accounting for less than 1% of all anorectal cancers and approximately 0.3% of all malignant melanomas. This tumor presents unique diagnostic and therapeutic challenges owing to its rarity and aggressive behavior. We report two cases of primary anorectal melanoma managed at our institution between 2020 and 2023, along with a comprehensive literature review of current diagnostic and therapeutic approaches. Both patients were elderly men (72 and 63 years old) who presented with rectal bleeding as the primary symptom of their disease. Histological diagnosis was confirmed by positive immunohistochemical staining for Melan-A and S-100 proteins. Both patients presented with distant metastases at the time of diagnosis. One patient received palliative chemotherapy and died 9 months after diagnosis, while the other was lost to follow-up. Primary anorectal melanoma has a poor prognosis because of frequent metastasis at diagnosis. Recent advances in targeted therapy and immunotherapy have offered new therapeutic perspectives, although early detection remains crucial for improving patient outcomes.