The precise diagnosis of malignant small round cell tumors (MSRCTs) in fine-needle aspiration (FNA) cytology is a challenge that requires ancillary investigations. In this study, the authors evaluated the applicability of flow-cytometric immunophenotyping (FCI) and compared it with immunocytochemistry (ICC) for the accurate categorization of MSRCTs.
In total, 37 consecutive MSRCTs that had been diagnosed with FNA cytology were analyzed by ICC and FCI using a panel of antibodies against desmin, vimentin, CD99/major histocompatibility class I-related antigen 2, neuron-specific enolase, and pancytokeratin. The final diagnoses included Ewing sarcoma (n = 17), rhabdomyosarcoma (n = 6; 4 embryonal and 2 alveolar subtypes), neuroblastoma (n = 10), desmoplastic small round cell tumor (n = 2), and retinoblastoma (n = 2).
Accurate categorization was possible in 67.5% of cases by ICC and in 64.8% of cases by FCI. Concordant immunophenotyping results with either technique were obtained in 21 cases (59.4%). Low cellularity of the sample and negativity for all markers tested were some limitations to both techniques when applied on fine-needle aspirates. However, using a combination of both techniques, 86.4% (32 of 37 cases) MSRCTs were typed accurately.
FCI is applicable on FNA material and complements ICC in accurate the typing of MSRCTs. This is particularly useful in advanced-stage disease, when neoadjuvant chemotherapy may be instituted promptly.