CD99 and central nervous system neoplasm: Of particular interest will be a future comparison with PATZ1-fused tumors occurring in non-CNS sites, to investigate the possibility of a common neuroectodermal/neural crest progenitor cell that may also be of relevance in the formation of the previously described sarcomas (although markers of EWSR1:PATZ1 sarcomas such as CD99, desmin and myogenin were not found to be expressed in the CNS tumors).