Combination tumors of the nervous system: A single-center analysis of a rare condition and comprehensive review of the literature.

Background: With less than 650 published cases, combination tumors of the nervous system, that is, two locally intertwined but histologically distinct tumor entities, pose a rare constellation, its clinical relevance still being a matter of debate. Methods: A consecutive cohort of 2530 patients operated on meningioma or hemangioblastoma between 2009 and 2021 was retrospectively screened for concomitant neoplastic disease to identify cases of combination tumors. Additionally, all available literature published between 1930 and 2021 was compiled in a comprehensive review. Results: Our cohort comprised 144 cases of patients with concomitant neoplastic disease and among those 10 instances of combination tumors. Another instance occurred after our screening period. Benign entities were meningiomas, but no hemangioblastoma. Contributing tumors were adenocarcinomas, lymphoma, glioblastoma, pituitary neuroendocrine tumors, and neurinoma. Patients' age ranged from 41 to 81 years with a slight preference for females. Identification of concomitant neoplasia was first achieved due to the combination tumor in about half of our cases. For the rest, median latency until manifestation of the combination tumor was 9 years. The odds ratio for a combination tumor was 17.6 for meningioma patients with known concomitant neoplasia, but it was preoperatively suspected in 18.2% of cases only. Conclusion: Presenting one of the largest clinical series, we provide evidence that known concomitant neoplasia in patients with suspected meningioma should make clinicians consider a combination tumor. Confirmation may lead to therapeutic consequences, largely contributing to long-term prognosis. Furthermore, we present the most extensive literature review on the matter to date.