Subependymoma in the lateral ventricle incidentally detected by routine brain examination--case report.

A 42-year-old male visited our hospital for a routine brain examination, which incidentally identified an intraventricular mass lesion (2.7 x 1.6 x 1.2 cm3). Magnetic resonance imaging showed the tumor was isointense on the T1-weighted image and hyperintense on the T2-weighted and proton images. The intraventricular tumor was totally extirpated through the interhemispheric ipsilateral transcallosal approach. The histological diagnosis was subependymoma. Neuroimaging cannot differentiate this benign neoplasm from other more aggressive tumors. Widespread use of the medical checkup system is expected to find a higher incidence of otherwise non-identified asymptomatic lesions. Surgical extirpation is one of the treatment options to establish the correct diagnosis and to prevent symptoms.