Over the past few decades, our understanding of the molecular underpinning of primary neoplasms of the central nervous system (CNS) has progressed substantially. Thanks in large part to this expansion in our knowledge base, the World Health Organization (WHO) has recently updated its classification of tumors of the CNS. 1 One of the key elements of this update was the inclusion of molecular diagnostic criteria for the classification of infiltrating gliomas. While the previous classification system was based upon histologic subtypes of the tumor (astrocytoma, oligodendroglioma, and oligoastrocytoma), the revised classification system incorporates molecular testing to establish the genetic characteristics of the tumor to reach a final integrated diagnosis.
In this article, we present 3 cases to highlight some of these recent changes in the WHO diagnostic categories of primary CNS tumors and to illustrate the role of specific molecular tests in reaching a final integrated diagnosis. We then propose a clinical practice guideline for the Veterans Health Administration (VHA) that recommends use of molecular testing for veterans as part of the diagnostic workup of primary CNS neoplasms.