Mixed epithelial and stromal tumor of the kidney: a rare case report and review of the literatures.

Mixed epithelial and stromal tumor of the kidney (MESTK) is a rare complex renal neoplasm composed of a mixture of cystic and solid components. Until date only few cases of MESTK have been reported. We present here a rare case of MESTK that was diagnosed in a 56-year-old female. The patients were referred to our hospital due to a mass on the right kidney identified incidentally in a routine physical examination. A pre-operative diagnosis of cystic renal cell carcinoma was made and a right radical nephrectomy was carried out. Macroscopically, a cystic tumor was noticed in the upper portion of the right kidney. Various-sized cysts accompanied by multiple cysts and few solid areas were observed. Immunohistochemically, various epithelial markers as well as stromal markers were identified. Taken together with all the immunohistochemical results and morphological pattern of the tumor, a diagnosis of MESTK was made. MESTK is relatively rare and generally benign. However, it is difficult to distinguish between benign or malignant tumors according to the current radiological method. Therefore a complete resection of the tumor by partial or radical nephrectomy is suggested.