Pilocytic astrocytoma with abundant oligodendroglioma-like component.

An 18-year-old girl presented with a history of visual disturbance without headache, nausea, or vomiting in May 2010. In July 2010, the patient visited our hospital because of visual disturbance. Head magnetic resonance images revealed hydrocephalus caused by a ring-enhancing mass lesion located in the vermis. Total tumor removal was performed. Histological findings revealed that honeycomb cells resembling oligodendrocytes accounted for most parts of the tumor. Rosenthal fibers and hyaline droplets were seen in a small portion. The tumor cells were immunoreactive for GFAP and Olig2, but none of the tumor cells were immunoreactive for Symaptophysin, EMA, or IDH 1. according to these findings, the tumor was diagnosed as pilocytic astrocytoma with an abundant oligodendroglioma-like component. Pilocytic astrocytoma is known to be associated with an oligodendroglioma-like component; however, the differential diagnosis for oligodendroglioma may be difficult when an oligodendroglioma-like component occupies most of the tumor.