Concurrent intraventricular intracranial myxoid mesenchymal tumor and ependymoma in a long-term Ewing sarcoma survivor.

Intracranial myxoid mesenchymal tumor, FET::CREB fusion positive is a rare, recently described central nervous system neoplasm. It is characterized by EWSR1::CREB family transcription factor fusion, typically arises in children and adolescents, and is locally aggressive even after gross total resection. Currently, there are little data available to guide management and gauge long-term prognosis. Furthermore, there have been no reports of these lesions occurring simultaneously with other intracranial neoplasms or in patients with a history of malignancy. Here we describe the first case of a very unusual patient with intracranial myxoid mesenchymal tumor of the right lateral ventricle with a concurrent fourth ventricular ependymoma who had a remote history of Ewing sarcoma of the right fibula.