Aspiration cytology of Wilms' tumor.

We reviewed the cytomorphologic features of fine needle aspiration biopsy (FNAB) smears from 15 cases of renal, extrarenal and metastatic Wilms' tumor. The findings were correlated with the histopathologic features. In cytology smears, blastemal cells were recognized in all cases. The following cell types were seen: epithelial cells, 60%; stromal component, 33.3%; tubular differentiation, 26.6%; and glomeruloid differentiation, 33.3%. FNAB smears of the metastatic lesions in the liver and of the primary lesions did not reveal any significant difference in cellular composition. Subcutaneous soft tissue metastasis from an anaplastic Wilms' tumor showed marked anaplasia and pleomorphism of blastemal cells along with frequent mitosis and bizarre tumor giant cells. Extrarenal Wilms' tumor showed only blastemal cells, though histopathology showed the classic triphasic pattern along with skeletal muscle differentiation. There were no complications attributable to the procedure. Recognition of these cellular components in FNAB smears will help in establishing an FNAB diagnosis of Wilms' tumor, particularly when preoperative chemotherapy is needed.