Beside playing an important role in the regulation of stemness, under the control of the Nanog transcription factor in mouse embryonic stem cells [12,13,14], it is also expressed in Ewing sarcoma/primitive neuroectodermal tumor (PNET), in which it is up-regulated by the fusion transcript EWS-FLI1, promoting cell proliferation and inhibiting apoptosis [12,13,15]. The gene discussed is EWSR1; the disease is primitive neuroectodermal tumor.