Rhabdoid tumors (RT) are rare, renal or extrarenal, high-grade malignancies. The cytologic diagnosis may be confirmed if combined with genomic results. In the current study, the authors present the cytologic and ancillary techniques used to diagnose RT in their series of 20 tumors in 13 patients.
Clinical charts as well as cytologic, histologic, karyotypic, and molecular biology results were reviewed.
Twelve fine-needle aspirations (FNAs) were performed for primary diagnosis, 7 were to confirm a metastasis, and 1 was to confirm local recurrence. Primary tumors were in the kidney in 7 cases and 13 were extrarenal. Patient age ranged from 5 months to 26 years. There were 7 females and 6 males. FNAs were cell-rich in 16 cases and cell-poor in 4 cases and revealed a mix of atypical spindle-shaped, round, rhabdoid, or epithelioid cells, singly or in clusters. Mitosis and necrosis occasionally were present. The original cytologic diagnosis was malignant in all cases. There were no unsatisfactory or false-negative samples. In the 12 primary tumors, the preliminary FNA diagnosis was RT in 7 cases (58%), rhabdomyosarcoma in 4 cases (33%), and malignant peripheral nerve sheath tumor in 1 case (8%). Karyotypes were available in 6 cases, 3 of which demonstrated chromosome 22 changes. Fluorescence in situ hybridization revealed loss of probe signals for the SMARCB1 gene locus in 5 cases; DNA sequence analysis performed in 9 cases revealed deletions in codons of the SMARCB1 gene in 7 cases and a mutation in 2 cases.
The primary diagnosis of RT is possible on FNA. In the current study, 12 of 13 cases were diagnosed by FNA with a combination of clinical information, immunocytochemistry, and molecular analysis.