Exophytic Cerebellar Glioblastoma in the Cerebellopontine Angle: Case Report and Review of the Literature

We report the unique case of a 69-year-old man with a cerebellar glioblastoma showing an exophytic growth pattern. Magnetic resonance imaging revealed a heterogeneously gadolinium-enhancing tumor in the right cerebellopontine angle. The preoperative differential diagnoses included an intraaxial tumor, such as high-grade glioma, and an extraaxial tumor, such as ameningioma or neurinoma. The tumor with a clear boundary was subtotally removed, except for the adhesion site to the petrosal vein, and the histologic diagnosis was glioblastoma. Immunohistochemical analyses demonstrated that the tumor cells were immunopositive for epidermal growth factor receptor and immunonegative for p53 mutation and IDH1 R132H, indicating that it had different genetic features from a typical cerebellar glioblastoma. Conventional radiotherapy with 60 Gy concurrent with temozolomide was performed, and the condition of the patient has remained stable for 24 months since the operation. Exophytic cerebellar glioblastoma should be considered in the differential diagnosis of cerebellopontine angle tumor.