Ezrin immunohistochemical expression in chondrosarcomas, osteosarcomas and Ewing sarcoma family of tumors

Abstract

Dear Sir, Ezrin immunohistochemical (IHC) expression has been described in bone sarcomas, being present mainly in osteosarcomas [1–5]. Salas et al. [4] described the utility of ezrin protein expression as a tool to differentiate between conventional chondrosarcomas and chondroblastic osteosarcomas, demonstrating a specificity of 100%. In the present study, we describe ezrin IHC expression in 397 bone tumors, including 33 osteosarcomas (eight lowgrade, 20 high-grade and five chondroblastic), 23 conventional chondrosarcomas (ten grade I, eight grade II and five grade III) and 341 Ewing sarcoma family of tumors (ESFT) [236 conventional, 42 primitive neuroectodermal tumor (PNET) and 63 atypical]. The sections were immunostained with ezrin antibody (clone 3C12, dilution 1:250). The cytoplasmic/membranous immunoexpression was scored as negative ( 50%). For the statistical analysis, negative and poor ezrin tumors were considered as negative, and moderate and intense ezrin tumors were considered as positive. Chi-square or Fisher’s exact test was performed for statistical analysis. Ezrin immunoexpression was heterogeneous in the present series. Ezrin stained in a higher proportion of analyzed osteosarcomas cases (69%) than ESFT (40.7%) and chondrosarcomas (30%, p=0.023) (Figs. 1, 2, 3). Interestingly, chondroblastic osteosarcoma tumors did not reveal ezrin expression (Fig. 2), and some cases of low-grade chondrosarcoma revealed poor ezrin immunoexpression; both results are in contrast with the study of Salas et al. [4]. However, similar to the results obtained by Salas et al. [4], the protein immunoexpression in the present series is associated with the histological grade, being higher in morphologically high-grade tumors. Highgrade osteosarcomas and chondrosarcomas stained ezrin in a higher proportion (95% and 100%, respectively, p< 0.001) than low-grade osteosarcomas and chondrosarcomas. Within the ESFT, ezrin expression was higher in atypical ESFT (58.9%, p<0.001) and PNET (58.6%, p<0.001) than in conventional ESFT (30%). The immunostaining in chondrosarcoma and osteosarcoma was mainly cytoplasmic, but several cases in ESFT also displayed a membranous pattern similar to CD99 expression. In ESFT with strong ezrin expression, apoptotic cells did not express ezrin compared with non-apoptotic cells (Fig. 3). In conclusion, based upon present experience, I. Machado : S. Navarro : F. Giner :A. Llombart-Bosch (*) Pathology Department, University of Valencia, Avda Blasco Ibanez 17, 46010 Valencia, Spain e-mail: Antonio.llombart@uv.es