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.
Purpose
In 2013 the VHA National Director of Pathology & Laboratory Medicine Services (P&LMS) chartered a national molecular genetics pathology workgroup (MGPW) that was charged with 4 specific tasks: (1) Provide recommendations about the effective use of molecular genetic testing for veterans; (2) Promote increased quality and availability of molecular testing within the VHA; (3) Encourage internal referral testing; and (4) Create an organizational structure and policies for molecular genetic testing and laboratory developed tests. The workgroup is currently composed of 4 subcommittees: genetic medicine, hematopathology, pharmacogenomics, and molecular oncology. The molecular oncology subcommittee is focused upon molecular genetic testing for solid tumors.
This article is intended to be the first of several publications from the molecular oncology subcommittee of the MGPW that address some of the aforementioned tasks. Similar to the recent publication from the hematopathology subcommittee of the MGPW, this article focuses on CNS neoplasms.2
Scope of Problem
The incidence of tumors of the CNS in the US population varies among age groups. It is the most common solid tumor in children aged < 14 years and represents a significant cause of mortality across all age groups.3 Of CNS tumors, diffuse gliomas comprise about 20% of the tumors and more than 70% of the primary malignant CNS tumors.3 Analysis of the VA Central Cancer Registry data from 2010 to 2014 identified 1,186 veterans (about 237 veterans per year) who were diagnosed with diffuse gliomas. (Lynch, Kulich, Colman, unpublished data, February 2018). While the majority (nearly 80%) of these cases were glioblastomas (GBMs), unfortunately a majority of these cases did not undergo molecular testing (Lynch, Kulich, Colman, unpublished data, February 2018).
Although this low rate of testing may be in part reflective of the period from which these data were gleaned (ie, prior to the WHO release of their updated the classification of tumors of the CNS), it is important to raise VA practitioners’ awareness of these recent changes to ensure that veterans receive the proper diagnosis and treatment for their disease. Thus, while the number of veterans diagnosed with diffuse gliomas within the VHA is relatively small in comparison to other malignancies, such as prostatic adenocarcinomas and lung carcinomas, the majority of diffuse gliomas do not seem to be receiving the molecular testing that would be necessary for (1) appropriate classification under the recently revised WHO recommendations; and (2) making important treatment decisions.