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

We report a case of an unusual sar-coma arising in the ovary of an infant g irl. Histologically, the tumor was composed of clear, undifferentiated cell s set in an arborizing vascular stroma. Immunohistochemical staining was po sitive only for vimentin. Ultrastructural evaluation demonstrated undiffere ntiated cells with interdigitating broad cell processes that encompassed ir regular electron lucent spaces that contained flocculent extracellular mate rial. Light and electron microscopic features of the tumor resembled a clea r cell sarcoma of the kidney. Although the cell of origin is unproven, both tumors may arise from primitive mesenchymal cells that may not be restrict ed to the kidney.