Collision tumor comprised of chronic lymphocytic leukemia and myxopapillary ependymoma

Collision tumors involving the co-occurrence of two morphologically and genomically distinct neoplasms in the same anatomical site are exceptionally rare in the central nervous system (CNS). We report a unique case of a CNS collision tumor comprising chronic lymphocytic leukemia and myxopapillary ependymoma in a 77-year-old male with acute neurological decline. Presumed to represent leukemic infiltration, urgent laminectomy was pursued for tissue diagnosis and spinal cord decompression, revealing the unexpected ependymal component. This case highlights the diagnostic and therapeutic challenges inherent to managing collision CNS tumors, particularly when one neoplasm is hematological.