Ovarian sarcoma with pathologic features of clear cell sarcoma of the kidney.

We report a case of an unusual sarcoma arising in the ovary of an infant girl. Histologically, the tumor was composed of clear, undifferentiated cells set in an arborizing vascular stroma. Immunohistochemical staining was positive only for vimentin. Ultrastructural evaluation demonstrated undifferentiated cells with interdigitating broad cell processes that encompassed irregular electron lucent spaces that contained flocculent extracellular material. Light and electron microscopic features of the tumor resembled a clear cell sarcoma of the kidney. Although the cell of origin is unproven, both tumors may arise from primitive mesenchymal cells that may not be restricted to the kidney.