Pure cystic nephroblastoma of the ovary with a review of extrarenal Wilms' tumors.

A second case of pure ovarian extrarenal Wilms' tumor (EWT) is presented. A clinical stage Ic tumor occurred in the right ovary of a 21-year-old female and corresponded to a 19-cm multilocular mass which histologically was a cystic, partially differentiated Wilms' tumor, closely resembling the highly differentiated metanephric adenoma. This pattern is reported for the first time in an ectopic location. At the interface between epithelial nests and ovarian tissue, plaques of alpha-inhibin positive cells were detected that corresponded to foci of peripheral stromal luteinization. Differential diagnosis with entities such as retiform Sertoli-Leydig cell tumors and with adenosarcoma should be made. The literature on EWT is also reviewed.