Although NKX2.2 immunohistochemistry and EWSR1 rearrangement studies were not available in our setting to definitively exclude BCOR- or CIC-rearranged sarcomas, the characteristic morphology and diffuse membranous CD99 positivity strongly supported the diagnosis of Ewing sarcoma (Figures 1, 2). The gene discussed is EWSR1; the disease is Ewing sarcoma.