Mixed epithelial and stromal tumors of the kidney: an overview.

Mixed epithelial and stromal tumor of the kidney is a recently recognized distinct neoplasm that should be distinguished from other renal neoplasms. These tumors are relatively rare with a female preponderance. Imaging studies are not diagnostic but reveal a solid or solid and cystic mass in most cases. Histopathologically, these tumors reveal biphasic growth pattern comprising mesenchymal and epithelial elements with characteristic estrogen and progesterone receptor immunoreactive mesenchyme reminiscent of ovarian stroma. Malignant transformation, recurrence, and metastasis are rare; however, recently a few cases of malignant mixed epithelial and stromal tumors have been reported in the literature. Recently a case with translocation t(1;19) has been described. This article provides a brief overview of the current knowledge of mixed epithelial and stromal tumor of the kidney.