Metastatic gastric tumor from renal cell carcinoma.

Metastatic tumors of the stomach are rare, with an incidence of 0.2%-0.7%, and they have been reported to result mainly from primary breast cancers, lung cancers, and melanoma. Further, among such metastatic tumors, the metastasis of renal cell carcinoma (RCC) to the stomach is an extremely rare disease, and it is usually reported in autopsy series. We report a rare case of metastatic gastric tumor derived from right renal carcinoma. Gastric endoscopy confirmed a large, polypoid, friable mass (type 1 tumor, about 7 cm in diameter) in the middle part of the stomach body. The mass was surgically excised and pathological examination showed that the gastric tumor was derived from a metastasis from the right kidney, because it was composed of malignant cells that were identical to those from the removed RCC. In addition, the tumor cells were immunoreactive for CD10, CD15, Ecadherin, early membrane antigen (EMA), and vimentin, but no reactivity was observed for cytokeratins 7 and 20 or c-KIT. Although gastric metastatic tumor derived from renal carcinoma is rare, the precise pre- and postoperative diagnosis may be important; thus, investigation for such metastatic tumors should be performed routinely in the follow up of patients who have been treated for RCC.