Unveiling the Rarity: A Case Report of Malignant Melanoma of the Rectum

Malignant melanoma of the rectum is an aggressive malignant tumor with anal pain and rectal bleeding as common clinical symptoms with a low incidence. Intestinal metastases are a common form of cutaneous melanoma. On a cellular level, the fibrous stroma is observed to be in the form of compact nests with a signet ring-like appearance. This is a case of a 67-year-old male with major complaints of altered bowel habits, a history of rectal bleeding for four months, and pain during defecation. Upon digital rectal examination, nearly half of the anal lumen was occupied by a fleshy mass. A detailed examination showed an ulcerating, black-colored nodule extending from the anorectal junction. Imaging studies confirmed a polypoidal lesion in the distal rectum. Histopathological examination of the biopsies revealed features consistent with malignant melanoma, supported by positive staining for HMB-45 and S-100 markers. The patient underwent an open abdominoperineal resection, followed by postoperative management and the initiation of chemotherapy. This case can be noted as underscoring the criticality of the diagnosis and treatment of rectal malignant melanoma and highlighting the importance of early recognition for improved patient outcomes.