Pathology of low- and intermediate-grade gliomas

Under the current World Health Organization (WHO) classification, gliomas can be divided into diffuse variants such as astrocytoma, oligodendroglioma, and mixed oligo-astrocytoma versus more discrete subtypes such as pilocytic astrocytoma and other less common entities. These tumors have been assigned histologic grades ranging from I to IV to reflect expected biological behavior. The ever-growing body of literature on genetic alterations of glial neoplasms promises to augment therapeutic and prognostic information in the future. An important example is the 1p and 19q deletions in oligodendrogliomas that recently have been associated with chemosensitivity and prolonged patient survival. This article reviews the pathology of low- and intermediate-grade gliomas, highlighting practical diagnostic and prognostic issues.