Subependymoma - lateral ventricle

Case contributed by Royal Melbourne Hospital


Admitted to the emergency department following a 60km/h MVA. HIV positive.

Patient Data

Age: 50 years
Gender: Male

Left scalp laceration noted. 

No intracranial hemorrhage identified. Grey white matter differentiation is preserved. An irregular, heterogenous, 27 mm, intraventricular mass is seen within the right lateral ventricle, possibly arising from the septum pellucidum. It does not show calcification. Mild prominent of the right lateral ventricle is probably due to normal asymmetry. Foramen magnum appears full however I note that the fourth ventricle is not dilated

A large intraventricular mass is seen within the right lateral ventricle in the region of the foramen of Monro measuring 27.2 x 15.5 x 23.1 (AP x W x H) mm. This is hyperintense on both FLAIR and T2 weighted imaging with some focal cystic areas which follow CSF. The lesion is isointense on T1 weighted imaging with no contrast enhancement. No susceptibility artefact is seen and no calcification is identified on retrospective review of the CT brain.

There is asymmetry of the lateral ventricles with dilatation of the right temporal horn suggesting a degree of ventricular entrapment. Periventricular signal change is felt more likely to represent small vessel ischemia rather than transependymal edema. The basal cisterns appear unremarkable.

The cerebellar tonsils have a PEG like configuration and extent proximally 9.5 mm below the foramen Magnum. Remaining posterior fossa structures, mid brain and corpus callosum appear unremarkable. No syringohydromyelia is identified in the upper cord.


  1. Right lateral ventricle intraventricular mass most likely represents a subependymoma or central neurocytoma. Ependymoma is felt unlikely given the lack of enhancement. Mild dilatation of the right lateral ventricle suggests a degree of outflow obstruction. This appears stable compared to the previous CT brain.
  2. Changes consistent with a Chiari I malformation.

 MACROSCOPIC DESCRIPTION: A nodule of gelatinous pale tan tissue 28x22x12mm.

MICROSCOPIC DESCRIPTION: Paraffin sections show a circumscribed moderately hypercellular tumor. This is composed of a mixture of nucleus-rich and poor regions, the latter being composed of tumor cell processes. Tumor cells have uniform round and oval nuclei with an open chromatin arrangement. No mitotic figures are seen and there is no vascular endothelial cell hyperplasia and no necrosis. Occasional poorly formed perivascular pseudorosettes are identified. Tumor cells show strong immunostaining for GFAP (not shown). No staining for epithelial membrane antigen (EMA) or synaptobrevin is seen (not shown). The features are of subependymoma. The topoisomerase (not shown) labeling index is approximately 1%.

DIAGNOSIS: Intraventricular tumor:  Subependymoma  (WHO Grade I)

Case Discussion

This case elegantly highlights how similar subependymomas can appear on imaging to central neurocytomas

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