Abstract: Anorectal malignant melanoma is a rare and highly aggressive malignant tumor,often misdiagnosed as benign conditions such as rectal polyps or thrombosed hemorrhoids.In this case,the patient underwent 3D laparoscopic abdominoperineal resection for rectal cancer at our hospital on April 16,2024,with pathological examination confirming malignant melanoma.As of August 9,2024,contrast-enhanced computed tomography of the chest and abdomen and magnetic resonance imaging of the whole abdomen suggested multiple systemic metastases.This underscores that patients with malignant melanoma are often at an advanced stage at the time of clinical presentation.Current treatment primarily involves surgery combined with various adjuvant therapies;however,the prognosis remains poor.The cornerstone of management lies in early recognition and timely intervention.

Key words: anorectal malignant melanoma； immunohistochemistry, therapy, case report