Anaplastic astrocytoma in the cerebellopontine angle

In this paper we present a case of glioma which was located in the cerebellopontine angle. The patient, a 3-year-old male, experienced difficulty with gait for one month before admission. He was admitted to Toyota Memorial Hospital on February 2, 1991, suffering from severe headache and vomiting. Neurological examination upon admission revealed horizontal nystagmus and ataxia. MRI revealed a mass in the cerebellopontine angle. Craniotomy was performed on February 4, 1991, and a tumor was revealed in the cerebellopontine angle. The tumor was clearly demarcated and encapsulated; the cerebellum and brainstem were compressed without damage. Most of the tumor was removed. A histopathological summary of the tumor follows. The tumor appeared as exophytic lesions on the pons, extending into the cerebellopontine angle. Tumor cells contained small round nuclei and acidophilic cytoplasm. The oncocyte, which was growing endomorphically, revealed a short-cell projection, suggesting a tendency to penetrate blood vessels. Intercellular microcystic degeneration was observed clearly, with some parts of the oncocyte forming a myxoid matrix. Immunohistochemically, most of the tumor cells reacted positively to Vimentin, but negatively to S-100 protein and GFAP. Given the pathological information, the tumor was interpreted as anaplastic astrocytoma. Postoperative radiation therapy was performed, but the patient died four months later because the tumor had spread to the brainstem. In this paper we discuss the differential diagnosis of the cerebellopontine angle tumor and the appearance of anaplastic astrocytoma as exophytic lesions on the pons and the spread of the tumor into the cerebellopontine angle.