RESUMO
Primary malignant melanoma of the colon is an extremely rare tumor due to the absence of melanoblasts in this segment of the digestive tract. We report the case of a patient presenting an ulcerated lesion with a neoplastic appearance in the dentate line during a coloscopy. After chemotherapy and radiotherapy, surgical amputation was performed. The study of the surgical specimen described an invasive malignant melanoma located in the submucosa without involvement of the overlying epithelium or the muscularis propria, nor vascular or lymph node invasion, and with tumor free margins. The patient was presented to the melanoma committee, which determited follow up in consultations. This case strengthens the importance of a good anatomopathological study to prevent delays in diagnosis and appropriate treatment.