Sarcoma: Radiologic Manifestations of This Newly Defined Pathologic Entity

SUMMARY: Although these entities are histologically similar, recent advances in molecular genetics have allowed the distinction of central nervous system extraosseous Ewing sarcoma (CNS-EES) from central primitive neuroectodermal tumors (c-PNET) including medulloblastoma and supratentorial PNET. We present 2 cases of pathologically confirmed CNS-EES. Knowledge of CNS-EES as a distinct entity enables the neuroradiologist to suggest the proper diagnosis and the need for special immuno-histochemical and molecular studies to confirm the diagnosis. Because treatment and prognosis are vastly different, the proper diagnosis of CNS-EES versus c-PNET is critical. Ewing sarcoma (ES) is usually identified as a primary ma-lignancy of bone with soft-tissue extension. Tefft et al1 de-scribed the first series of patients with soft-tissue tumors that histologically resembled ES, with no clear osseous involve-ment. This group of tumors is currently recognized as ex-traosseous Ewing sarcoma (EES); it commonly involves the paravertebral regions of the spine and has only rarely been noted to involve primarily the central nervous system (CNS).2 Currently diagnosis of the ES family of tumors is reliably base