Histopathological picture of the tumor was similar to the one described previously, with round, small undifferentiated cells with high mitotic activity and hyperchromatic nuclei, suggesting primitive neuroectodermal origin, yet the positive sensitive immunohistochemical markers of ES, i.e., CD99 and NKX2.2, in our case series supported the diagnosis of ES as described in literature.8-10. This evidence concerns the gene CD99 and Ewing sarcoma.