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I

Primary melanoma originating in the gastrointestinal tract is very rare and the majority of these tumors arise in the mucosa of the anus or rectum. A case of solitary colonic melanoma in a 79-year-old man is described with a review of pertinent literature. The surgically excised neoplasm was evaluated by routine histology and immunohistochemistry stains. Pathologic examination of the excised cecal mass revealed an 8 x 5-cm tan-pink mass with a central green-black necrotic area. Histologically, there were solid sheets of S100- and HMB-45-positive pigmented cells extending from the mucosal ulcerated surface through the bowel wall. The patient had no evidence of cutaneous or ocular primary melanoma. He remained free of recurrent disease 5 years after surgical resection of the colonic melanoma. The unique pathologic features and clinical outcome support the diagnosis of primary colonic melanoma in this patient.

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