Metastatic Clear Cell Renal Cell Carcinoma Presenting as Multiple Colonic Polyps

A 92-year-old male presented for routine endoscopic surveillance of his gastrointestinal (GI) tract. He did not have any GI symptoms currently, and the patient had undergone a right nephrectomy for renal cell carcinoma 17 years previously. A lower GI endoscopy revealed polyps in the ascending colon, hepatic flexure, and sigmoid colon (2 polyps). All the polyps were snared and removed in toto. Histological evaluation of all 4 polyps showed similar features. There was expansion of the lamina propria by sheets of clear cells arranged in a nested pattern with a rich vascular network. Immunohistochemistry showed the tumor to be positive for low-molecular-weight cytokeratin, CD10, and vimentin. The features were morphologically and immunophenotypically that of clear cell renal cell carcinoma. This case highlights an extremely unusual presentation of recurrent renal cell carcinoma as multiple, separate colonic polyps 17 years after resection of the primary tumor.