Role of immunocytochemistry and DNA flow cytometry in the fine-needle aspiration diagnosis of malignant small round-cell tumors

In the present study, DNA flow cytometry (FCM) and immunocytochemistry (ICC ) with a selected panel of antibodies were performed on 51 cases of maligna nt tumors which were referred for fine-needle aspiration biopsy (FNAB) to o ur Department of Cytology for the last 2 yr. Twelve cases were diagnosed as neuroblastoma, 16 as Ewing's sarcoma, 2 as retinoblastoma, 5 as non-Hodgki n's lymphoma (NHL), 5 as rhabdomyosarcoma, 2 as peripheral neuroectodermal tumors (PNETs), and 8 as Wilms' tumor. Eleven of 12 neuroblastomas were diploid by FCM, and 1 was aneuploid, with an S-phase fraction (SPF) of 8.3%. Neuron-specific enolase (NSE) was negati ve in 3 and positive in 8 cases of neuroblastoma, whereas neuroblastoma mar ker was positive in 3/11. Sixteen of 17 Ewing's sarcomas were diploid, and 1 showed tetraploid aneuploidy, with an SPF of 10.06%. Eight of 13 Ewing's sarcomas were positive for Mic-2 gene product (Ewing's marker). All 5 NHL w ere positive for leukocyte-common antigen (LCA). Three of 5 rhabdomyosarcom as were diploid, and 2 cases showed aneuploidy. Rhabdomyosarcoma showed mus cle-specific actin positivity in 4 and desmin positivity in 3 cases. All 3 cases of PNET were diploid and positive for the Mic-2 gene product, whereas NSE and vimentin were positive in 2 cases. Both cases of retinoblastoma we re diploid. Immunostaining was noncontributory in 1 case, and the other sho wed positivity for the retinoblastoma gene product, NSE, and chromogranin. Seven of 8 Wilm's tumors were diploid, and 1 showed aneuploid, with an SPF of 11.13%. Seven of 8 Wilm's tumors were positive for cytokeratin (CK), 5 w ere positive for NSE, 6 were positive for epithelial membrane antigen (EMA) , and 5 were positive for vimentin. FNAB diagnosis of malignant round-cell tumors is difficult only by light mi croscopy. Due to the availability of specific markers for subgrouping tumor s, ICC has proved to be more useful these days, while DNA FCM has little di agnostic value, as most of them are diploid. Further ancillary studies, e.g ., electron microscopy, image analysis, and other molecular investigations, are required to further categorize these tumors more precisely for better clinical management of these cases. (C) 2001 Wiley-Liss, Inc.