Infratentorial low-grade oligoastrocytoma with aggressive clinical behavior in an adult: a case report with genetic characterization.

Oligoastrocytoma preferentially arises in the cerebral hemisphere, and a cerebellar location is unusual. We report the case of a 35-year-old woman with an aggressive cerebellar tumor histopathologically diagnosed as oligoastrocytoma World Health Organization (WHO) grade II. After partial removal of the tumor, she underwent concomitant temozolomide (TMZ) therapy with local irradiation followed by additional TMZ monotherapy. However, her symptoms gradually worsened, and chronological magnetic resonance imaging showed remarkable tumor enlargement. In accordance with the aggressive clinical course, unfavorable genetic characteristics such as the gain of the entire chromosome 7, loss of 9p, absence of 1p/19q codeletion, absence of methylation of the O6-methylguanine-deoxyribonucleic acid methyltransferase promoter, and absence of the isocitrate dehydrogenase-1 mutation were observed. The present case illustrates that these molecular characteristics represent the biological features of gliomas more closely than the histopathological diagnosis and may also suggest that infratentorial gliomas arise through a distinct tumorigenic pathway from their supratentorial counterparts.