Aggressive biological behavior of benign central nervous system neoplasms: The case of hemorrhagic subependymomas - An illustrated review.

Background: Subependymomas (SEs) are low-frequency, histologically benign tumors. Their association with hemorrhagic phenomena is extremely unusual. Methods: This is a literature review of pathologically verified reports of hemorrhagic SE (hSE), analyzing their epidemiological, clinical, diagnostic, therapeutic, and outcome features. This review includes an original illustrating report. Results: A total of 30 cases were analyzed. All but three patients presented unique hSEs growing predominantly within the lateral ventricles (86.6%). The pattern of associated hemorrhage was, in decreasing order of frequency, intratumoral (55.2%), mixed, and extratumoral. Symptoms at presentation, mainly of rapid onset (75%), derived from high intracranial pressure, meningeal irritation, and/or focal neurological impairment. Superficial siderosis was an exceptional complication, presumably produced after repeated bleeding. Most hSEs were misdiagnosed either as a more aggressive neoplasm (84.6%) or as a vascular malformation (7.7%) because of their invariably atypical, heterogeneous radiological appearance. Twenty-nine patients underwent surgical treatment, reaching total resection rates close to 80%. Nevertheless, high figures of both permanent disability (25%) and mortality (10.3%) were recorded at the last follow-up. Conclusion: Bleeding increases both the severity of initial clinical symptoms and the complexity of the radiological differential diagnosis of SEs but does not seem to influence strongly the degree of surgical resection of these otherwise histologically benign neoplasms. Both the exact topography of the hSE within the ventricular system and the presence of intraparenchymal extension of the neoplasm and/or the associated bleeding could negatively affect the final clinical outcome.