Metanephric adenosarcoma in a young adult: Morphologic, immunophenotypic, ultrastructural, and fluorescence in situ hybridization analyses - A case report and review of the literature

Metanephric neoplasms are uncommon renal tumors that arise in both children and adults. They may be composed of small epithelial cells or benign strom a, or both, and are termed metanephric adenoma, metanephric stromal tumor, or metanephric adenofibroma, respectively. Thus far, these tumors have been known for their benign behavior. We present the case of a 21-year-old woma n who developed a neoplasm composed of a renal epithelial component identic al to metanephric adenoma combined with a malignant spindle cell sarcoma. T he epithelial component was positive for pankeratin AE1/3, whereas the sarc omatous component was negative for epithelial markers and positive for vime ntin, CD34, and CD117. No smooth muscle differentiation was apparent in the sarcoma by immunohistochemistry or ultrastructural analysis. By fluorescen t in situ hybridization analysis of the sarcomatous component there was mon osomy of the X chromosome, but no apparent variation from the normal diploi d pattern for chromosomes 3, 7, 12, and 17. We conclude that the spectrum o f metanephric neoplasia should be expanded to include malignant stromal var iants, and we propose the term "metanephric adenosarcoma" for the present c ase.