Low-Grade Gliomas

Excerpt

Tumors of the central nervous system (CNS) are classified based on their cell lineage of origin. Gliomas are a type of neuroepithelial tumor that originates from the supporting glial cells within the CNS. Glial cell tumors are further classified based on involved cell types, for example, astrocytomas, ependymomas oligodendroglioma, and mixed oligoastrocytomas. Here in this review, diffuse gliomas with lower grade pathology, more specifically grade 2 (diffuse infiltrating) gliomas, are reviewed.

In 2016, the World Health Organization (WHO) published an updated version of the classification of CNS tumors. There has been a significant restructuring in classifying these tumors, and for the first time, molecular features are included in addition to the previously described histopathological features.

The histological features used include cytological atypia, mitotic activity, anaplasia, microvascular proliferation, and necrosis. All the features are present in high-grade gliomas, and either none or only cytological atypia in the lower-grade tumors. Low-grade gliomas (LGGs) are typically slow-growing tumors compared to high-grade gliomas. Over time, greater than 70% of these can transform into a higher grade or become aggressive in behavior within a decade.

A study on serial MRI scans before treatment showed that these lesions typically grow steadily at an average rate of 4.1 mm annually. The survival is relatively long in low-grade gliomas compared to the more aggressive types. Thus various factors should be considered, including the toxicity of chemotherapy, radiation therapy, and complications with surgical interventions to appropriately manage and improve overall outcomes.