Subependymoma: lateral ventricle
Incidentally detected lesion on sinus CT
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Large left lateral ventricle lesion, with internal cystic degeneration. Susceptibility images suggest calcification. A few foci of enhancement are seen, but the bulk of the lesion does not enhance. Obstruction of the foramen of Monro, with dilatation of the left lateral ventricle.
Eight fragments of white to pale tan, rubbery tissueranging in size from 6 x 5 x 2mm to 40 x 25 x 10mm.
Highly fibrillary glial lesion featuring clustered cell bodies accompanied by microcysts, with areas of prominent Rosenthal fibre formation, thromboed and scleroses blood vessels and old haemorrhage. Perivascular pseudorosettes are present focally. Mitotic figures are not seen. The lesion is separated from ventricular lining by a layer of white matter. Features qualify for subependymoma.
At the time of imaging, the differential included meningioma, but this would be expected to show more intense and homogeneous enhancement. Central neurocytoma was also considered, as it is commonly found in the lateral ventricles near the foramen of Monro, with 'bubbly' cystic areas. However moderate to strong heterogenous enhancement would be expected.
Although subependymomas are typically described in the inferior fourth ventricle, they also occur in the lateral, third ventricles and spinal cord. They are most commonly small, although can become large as in this case. Variable enhancement is seen (typically none to mild), but marked enhancement is also a feature (more commonly in the fourth ventricle than lateral ventricles). The most common demographics is in middle-aged to elderly males. In general, the diagnosis should be considered in a hyperintense ventricular tumor with poor enhancement (other ventricular tumors enhance more prominently).
They are WHO grade I tumors.