IDENTIFICATION OF CD56 AND CD57 BY FLOW-CYTOMETRY IN EWINGS-SARCOMA OR PRIMITIVE NEUROECTODERMAL TUMOR

CD56 and CD57 are commonly considered as natural killer and neuroectod ermal markers, but their expression has been identified in a wide spec trum of neoplasms including some cases of Ewing's sarcoma (ES) and pri mitive neuroectodermal tumor (PNET). We report two cases of small, rou nd blue cell tumor (SRBCT), in which flow cytometry immunophenotyping (FCI) detected strong expression of CD56 and CD57 (one case). Immunohi stochemical staining with Leu-19 and Leu-7 confirmed the FI results. A lthough CD56 and CD57 expression is consistent with ES/PNET, it can be potentially misleading if results of FCI are interpreted in the absen ce of other findings. These cases suggest the utility of FCI in undiff erentiated SRBCT. The literature on CD56 and CD57 expression in ES/PNE T is reviewed and discussed.