Bone metastasizing renal tumor (clear cell sarcoma) of childhood with epithelioid elements

A case of bone metastasizing renal tumor (clear cell sarcoma) of childhood (BMRTC) is presented. Histologic examination demonstrated the typical histopathologic features of this type of tumor. In addition, epithelial cells were present which occurred in groups, either around a central eosinophilic core or occasionally around a small central lumen. To the authors' knowledge, the presence of epithelial cells in BMRTC has not been reported before. The histogenetic implication of this finding is discussed.