Transformation of adult cerebellar pilocytic astrocytoma to glioblastoma.

A 54-year-old woman with a past history of uterine cancer developed a tumor in her right cerebellum. Magnetic resonance imaging with contrast enhancement revealed a mass composed of two components, inside and outside, although both components resided in the same high-intensity area on T2-weighted imaging. Surgical resection removed the bulk of the tumor. Pathological examination revealed two distinct pathological features of the tumor-the inner major component had the features of glioblastoma whereas outer minor component had those of pilocytic astrocytoma (PA). These two components occurred with intercalating transitional areas. No genetic differences, including BRAF alteration or IDH mutations, were detected in either component. Activation of Akt, which is reported to be associated with clinically aggressive and anaplastic PA was found in the PA component of this tumor. The transitional area also stained positive, suggesting the continuity of both components. Consequently, the glioblastoma in this case was likely to have developed as a result of malignant transformation of PA. This case provides additional support for the concept of anaplastic transformation of PA.