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Diffuse subependymoma of the bilateral lateral ventricles
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Received: ,
Accepted: ,
How to cite this article: Chen J, Yu X. Diffuse subependymoma of the bilateral lateral ventricles. J Clin Imaging Sci. 2026;16:19. doi: 10.25259/JCIS_268_2025
Abstract
A 55-year-old female presented with a persistent headache in the left parietal region for more than 2 months. Non-contrast computed tomography demonstrated irregular cast-like soft tissue densities along the walls of both lateral ventricles, with a cystic–solid mass located in the anterior horn of the left lateral ventricle. Magnetic resonance imaging findings strongly suggested a subependymoma involving both lateral ventricles. The patient underwent tumor resection, and histopathology confirmed subependymoma (World Health Organization Grade I) with cystic degeneration and hemosiderin deposition. This case is a rare diffuse subependymoma of both lateral ventricles with cystic degeneration and old hemorrhage. The clinical and imaging features are reported as follows.
Keywords
Computed tomography
Diagnosis
Magnetic resonance imaging
Subependymoma
INTRODUCTION
Subependymoma is a benign neuroepithelial tumor that originates from the subependymal glial layer and has ependymal differentiation characteristics, accounting for 0.2% to 0.7% of all intracranial tumors.[1] The 2021 World Health Organization classification of central nervous system tumors classifies it as a grade I tumor.[2] It is more common in middle-aged and elderly men and most frequently arises in the fourth ventricle, followed by the lateral ventricle near the foramen of Monro, and other locations are rare.[3] Patients are usually asymptomatic in the early stage. When the cerebrospinal fluid circulation is blocked by the tumor, it can be manifested as increased intracranial pressure or obstruction symptoms.[4] We report a case of subependymoma with diffuse distribution in both lateral ventricles to improve the understanding of this rare type of imaging findings.
CASE REPORT
A 55-year-old female presented with a persistent headache in the left parietal region for more than 2 months. Neurological examination was unremarkable. No lumbar puncture was performed as there was no clinical suspicion of infection or leptomeningeal disease. Non-contrast head computed tomography demonstrated cast-like soft tissue density lesions in both lateral ventricles with enlargement of the anterior horn of the left lateral ventricle. The lesion at the anterior horn was oval, with small cystic degeneration and punctate calcification [Figure 1]. Subsequent magnetic resonance imaging (MRI), including contrast-enhanced sequences, demonstrated diffuse abnormal signal lesions growing in a cast-like manner along both ventricular walls. The solid components of the lesions in the anterior horn of the left lateral ventricle showed iso- to low signal intensity on T1-weighted imaging (T1WI), high signal on T2-weighted imaging (T2WI) and fluid-attenuated inversion recovery Flair, and iso-intensity on DWI. Multiple small cystic changes and fluid–fluid levels were observed [Figure 2a-e]. On contrast-enhanced MRI, the solid component demonstrated punctate and small nodular mild enhancement, while the remaining lesions in the lateral ventricle showed no definite enhancement [Figure 2f]. The patient subsequently underwent surgical resection. Intraoperatively, the tumor was gray-white, soft in texture, and attached broadly to the ventricular wall. Histopathological examination revealed clusters and cords of uniform tumor cells embedded in a fibrillary matrix. Areas of cystic degeneration and hemosiderin deposition were observed. The overall features were consistent with subependymoma (WHO Grade I) [Figure 3].
DISCUSSION
Subependymoma is a rare intraventricular tumor, typically classified as WHO Grade I. It most commonly arises in the fourth ventricle and less frequently in the lateral ventricles, typically near the foramen of Monro. Diffuse bilateral involvement of the lateral ventricular walls, as observed in the present case, is distinctly uncommon.[5]
Radiologic teaching points and diagnostic considerations
The key radiologic teaching point in this case is that diffuse, cast-like subependymal growth along both lateral ventricular walls, accompanied by minimal enhancement and absence of diffusion restriction, should prompt strong consideration of subependymoma in the differential diagnosis.
In the present patient, several imaging features supported this diagnosis:
Cast-like growth along both lateral ventricular walls
Broad-based attachment to the ventricular wall without parenchymal invasion
Absence of peritumoral edema
No diffusion restriction on DWI
The solid component demonstrated overall mild enhancement, with a few focal punctate areas of more conspicuous enhancement.
Although both ventricular involvement and intratumoral hemorrhage may raise concern for infiltrative or malignant neoplasms, the lack of brain parenchymal invasion, preserved diffusion characteristics, and minimal enhancement suggested a slow-growing, low-grade lesion rather than an aggressive tumor. Recognition of this imaging constellation is essential to avoid overestimation of malignancy and unnecessary aggressive management.
Differential diagnosis
The main differential considerations for intraventricular tumors in adults include ependymoma, central neurocytoma, subependymal giant cell astrocytoma (SEGA), lymphoma, and metastasis.
Ependymomas usually demonstrate heterogeneous and moderate-to-marked enhancement of the solid component and cyst walls, frequently accompanied by significant mass effect and peritumoral edema. They may exhibit a more aggressive growth pattern with extension beyond the ventricular margins or invasion of adjacent brain parenchyma.[6] In contrast, the present lesion showed only mild punctate enhancement, no significant mass effect, no peritumoral edema, and no evidence of parenchymal infiltration, making ependymoma unlikely.
Central neurocytomas usually arise near the septum pellucidum and foramen of Monro, with a soap-bubble multicystic appearance on T2WI and heterogeneous enhancement on T1WI post-contrast imaging.[7] In this case, the lesion originated along the ventricular wall rather than the septum, and no diffusion restriction was observed.
SEGAs are typically associated with tuberous sclerosis complex and arise near the foramen of Monro, often demonstrating marked enhancement.[8] The absence of clinical features of tuberous sclerosis and the diffuse ventricular wall distribution make SEGA unlikely.
Primary central nervous system lymphoma or metastasis usually shows strong homogeneous enhancement and diffusion restriction due to high cellularity. The absence of restricted diffusion and limited enhancement in this case argues against these entities.
Impact on surgical planning
Pre-operative imaging played a crucial role in surgical planning. Diffuse bilateral ventricular wall involvement indicated multiple attachment sites, suggesting the need for piecemeal resection through a narrow surgical corridor. Contrast-enhanced MRI demonstrated multiple small peritumoral vascular structures, suggesting a relatively rich blood supply and a potential risk of intraoperative bleeding. Pre-operative awareness of these findings allowed early control of vascular pedicles to help minimize intraoperative blood loss.
Although both subependymomas have been reported in the literature, most cases present as discrete multifocal masses rather than diffuse cast-like growth along the entire ventricular wall.[3,5] The extensive subependymal distribution observed in this case closely mimicked infiltrative or malignant ventricular tumors, highlighting its diagnostic challenge and educational value.
CONCLUSION
This case represents a rare diffuse subependymoma involving both lateral ventricles, accompanied by cystic degeneration and old hemorrhage. MRI revealed cast-like growth along the lateral ventricular walls, mild enhancement, and multifocal cystic degeneration, with nodular enhancement on contrast imaging. The diagnosis was confirmed by post-operative histopathology. This case suggests that subependymoma should be included in the differential diagnosis of diffuse subependymal wall lesions.
Ethical approval:
Institutional Review Board approval is not required.
Declaration of patient consent:
The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given consent for their images and other clinical information to be reported in the journal. The patient understand that the patient’s names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Conflicts of interest:
There are no conflicts of interest.
Use of artificial intelligence (AI)-assisted technology for manuscript preparation:
The authors confirm that there was no use of artificial intelligence (AI)-assisted technology for assisting in the writing or editing of the manuscript and no images were manipulated using AI.
Financial support and sponsorship: Nil.
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