Collision tumor comprised of chronic lymphocytic leukemia and myxopapillary ependymoma

Background: 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). Case Description: 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. Conclusion: This case highlights the diagnostic and therapeutic challenges inherent to managing collision CNS tumors, particularly when one neoplasm is hematological.