RESUMO
Cystic nephroma (CN) is a benign cystic neoplasm composed of mixed epithelial and stromal elements. Less than 200 cases have been reported. We had a patient, a 41-year-old woman, who had a huge typical CN. The patient was admitted for a right renal mass that was found incidentally. On laparaoscopic right nephrectomy, there was an encapsulated 7 cm multilocular cystic mass at the upper pole. Microscopically, the cystic wall was lined by a single layer of low cuboidal or hobnail epithelium without a solid area. The thin septa were composed of bland, ovarian type spindle cells. The main differential diagnoses were mixed epithelial and stromal tumor (MEST), low grade multilocular renal cell carcinoma, and tubulocystic carcinoma. The results of immunohistochemical staining were cytokeratin 7/19(+/+) and CD10(-) in lining epithelium, estrogen receptor/progesterone receptor(+/+) in stromal cells. After surgery, she was free of recurrence for 10 months. We report this rare case and compare it with other cystic renal tumors, especially MEST.