A glioma is a common type of tumor that originates in the brain or spinal cord. While the public often perceives all brain tumors as highly aggressive, the behavior of gliomas can vary significantly. This variation depends on several factors, including the specific type of glial cell involved and how rapidly the tumor cells grow. Understanding these nuances is important for comprehending a glioma diagnosis.
What Are Gliomas
Gliomas are tumors that develop from glial cells, the supportive cells of the central nervous system (CNS). These cells, including astrocytes, oligodendrocytes, and ependymal cells, perform various functions that maintain a healthy environment for neurons. Glial cells provide structural support, supply nutrients, regulate the chemical environment, and form myelin, an insulating sheath that helps nerve signals travel quickly.
When glial cells grow uncontrollably, they form a mass known as a glioma. Gliomas are considered intra-axial brain tumors, growing within the brain’s substance and often intertwining with normal brain tissue. Their origin from supportive cells, rather than nerve cells, defines their fundamental nature.
Grading Gliomas
The World Health Organization (WHO) classifies gliomas using a grading system that indicates their aggressiveness and growth potential, ranging from Grade 1 to Grade 4. This system helps determine how the tumor might behave and guides treatment decisions. Grade 1 and Grade 2 gliomas are considered “low-grade” due to their less aggressive nature.
Grade 1 gliomas are slow-growing, often non-malignant, and are frequently associated with long-term survival, especially if completely removed surgically. These tumors have cells that appear very similar to normal cells. Grade 2 gliomas are also slow-growing but can sometimes recur as higher-grade tumors, indicating a potential for progression over time. While Grade 1 gliomas are often considered benign, Grade 2 gliomas are still a type of cancer but grow slowly and are less aggressive than higher grades. In contrast, Grade 3 gliomas are malignant with more abnormal cells and a tendency to spread. Grade 4 gliomas are highly aggressive and very malignant.
Features of Low-Grade Gliomas
Low-grade gliomas (WHO Grade 1 and Grade 2) exhibit distinct characteristics. These tumors demonstrate a slow growth rate, often taking years or even decades to enlarge. Under a microscope, the cells of low-grade gliomas appear less atypical and show fewer mitotic figures, indicators of cell division.
Another defining feature is their less invasive nature compared to high-grade gliomas, meaning they tend to have more defined borders. While Grade 1 gliomas can be well-defined, Grade 2 gliomas are often described as diffuse, meaning they can infiltrate surrounding brain tissue without clear boundaries. These biological characteristics, including their slow growth and less aggressive cellular appearance, contribute to their classification as less aggressive, offering a more favorable prognosis than higher-grade tumors.
Living with a Low-Grade Glioma
A diagnosis of a low-grade glioma begins with imaging tests such as Magnetic Resonance Imaging (MRI) or Computed Tomography (CT) scans to locate the tumor. However, a definitive diagnosis and grading require a biopsy, where tissue is analyzed under a microscope. This analysis determines the tumor type, its grade, and molecular features influencing prognosis and treatment.
Treatment approaches for low-grade gliomas prioritize preserving neurological function while managing the tumor. Initial treatment involves surgical removal of as much of the tumor as safely possible. In some cases, particularly for tumors in sensitive brain areas, a “watchful waiting” approach with regular MRI monitoring may be adopted, especially for patients without significant symptoms. Radiation therapy or chemotherapy might be considered when surgery cannot remove the entire tumor, for tumor progression, or for patients with certain risk factors. The prognosis for low-grade gliomas is more favorable than for high-grade gliomas, with median overall survival ranging from 5 to over 15 years. However, these tumors still require regular monitoring, as they can sometimes transform into a higher, more aggressive grade over time.