Adult Wilms' tumor. Intraoperative cytology and ancillary studies performed in a case as an adjunct to the histologic...

A case of blastema-predominant Wilms' tumor in a 64-year-old woman is reported. Intraoperative cytology of a renal mass was used to rule out malignant lymphoma and neuroendocrine carcinoma. Light and electron microscopy, immunocytochemical staining and flow cytometry (FCM) were also performed. Immunoperoxidase studies of smears showed positive staining for vimentin and negative staining for cytokeratins and epithelial membrane antigen. FCM DNA analysis of paraffin-embedded tissue showed no aneuploid peak. Frozen section interpretation of such tumors as seen in this case may be difficult, requiring distinction among several small-blue-cell neoplasms, including Wilms' tumor, neuroendocrine carcinoma and malignant lymphoma; intraoperative cytology can provide a valuable adjunct to frozen section diagnosis.