Metanephric adenoma of the kidney. A clinicopathologic, immunohistochemical and electron microscopic study of two...

We report two cases of metanephric adenoma in 40 and 48 year-old women. These rare kidney tumors were composed of cuboidal epithelial cells forming tubules, glomeruloid structures and sheets. Ultrastructural and immunohistochemical studies revealed that the tumor cells are similar to epithelial cells of developing nephrons. These features differentiate the metanephric adenoma from tubulo-papillary renal carcinoma, nephroblastoma, and cortical adenoma. According to its invariably benign course, the metanephric adenoma treatment could be restricted to a simple tumorectomy.