Subependymoma of the lateral ventricle--report of two cases.

Subependymoma is a rare benign tumor of the ventricular system. It was described as a distinct entity by Scheinker in 1945. The fourth ventricle is the most common location. Many cases are asymptomatic and discovered at autopsy. Symptomatic cases often present with hydrocephalus.We present two cases of subependymoma located in lateral ventricles. Case 1 was a 69-year-old male with non-Hodgkin's large Bcell lymphoma. He died following seizures and respiratory depression while he was receiving chemotherapy. At autopsy brain oedema and a small nodular mass located in the right lateral ventricular wall were discovered. Case 2 was a 38-year-old female presenting with headache. MR revealed a mass, approximately 2.5cm in diameter in the right lateral ventricle extending to the third ventricle. Both tumors were diagnosed as subependymoma. Microscopically, a fibrillary background, cell clusters with small uniform nuclei and rnicrocysts were the main histopathological characteristics. Microcysts contained slightly basophilic material stained with alcian blue pH2.5 and toluidine blue pH? This material was interpreted as extracellular mucin. Tumoral infiltration was positive for GFAP and S-100' protein. Ki-6? (MIB-l) proliferation index was lower than 1%. P53 was negative in both cases.