Intracranial Ewing sarcoma.

The occurrence of primary extraosseous Ewing sarcoma (EES) of the central nervous system (CNS) has only rarely been reported in the literature. It is important to distinguish this entity from the more common central primitive neuroectodermal tumor (PNET) of brain, since the management of these tumors is different from that of EES. We present the clinical, radiologic, and pathologic features of two cases of EES occurring in the brain. The diagnosis was further confirmed by detection of a rearrangement of the FLI1 and/or EWS gene loci in tumors from both patients using fluorescent in situ hybridization (FISH). Although rare, the possibility of EES should be considered particularly when tumors that arise near the meningeal surface of the brain and have the pathologic appearance of a PNET. Demonstration of t(11;22)(q24;q12) by molecular analysis essentially confirms the diagnosis and enables the oncologist to choose appropriate therapy.