Fine Needle Aspiration Cytology of Fetal Rhabdomyomatous and Teratoid Wilms Tumor

OBJECTIVE: To review nephrectomy specimens for pediatric renal tumors seen over a period of 9 years (1995-2003). STUDY DESIGN: Specimens categorized as fetal rhabdomyomatous Wilms tumors (WTs) or teratoid WTs were selected. Corresponding fine needle aspiration cytology slides were subjected to cytomorphologic analysis. RESULTS: Of 93 specimens of WT, 3 cases of fetal rhabdomyomatous WT and 2 cases of teratoid WT were identified. The aspirates were stromal predominant, and all of them showed rhabdomyoblasts embedded within. These stained variably green or orange on Papanicolaou stain and blue-gray on May-Grünwald-Giemsa stain. In all 5 aspirates, foci of blastema with or without tubules were identified, permitting a diagnosis of WT. A squamous morule was seen in an aspirate from teratoid WT. CONCLUSION: The outcome of fetal rhabdomyomatous and teratoid WTs is good, but the tumors do not shrink with chemotherapy. Identification of rhabdomyoblastic elements on aspirates can help in assessment of subsequent response to treatment.