Brain Cancer Grades

Cancer staging is a standardized process that evaluates the spread of a tumor beyond its site of origin, which is a key consideration when planning treatment. For many types of cancer, the most commonly used staging system is the American Joint Committee on Cancer (AJCC) TNM system, which considers the extent of the tumor (T), lymph node involvement (N) and metastasis (M).

Brain cancer does not behave in the same way as most other cancers. Although a primary brain tumor can potentially spread within the brain, it is unlikely to migrate outside of the brain or away from the central nervous system (CNS). Additionally, while other cancers typically do not change stages, brain cancer can progress to a more advanced grade over time. For these reasons, brain cancer is usually graded (rather than staged) based on the World Health Organization (WHO) grading system, which considers the cellular characteristics, growth patterns and aggressiveness of the tumor.

The unique grading approach for brain tumors allows for a more precise understanding of the nature of the cancer, which can aid in the development of highly refined treatment strategies.

The WHO brain cancer grading system consists of four distinct grades:

Grade 1 brain tumors

The least aggressive type of brain cancer, grade 1 brain tumors are localized, slow-growing and unlikely to invade surrounding tissues. When viewed under a microscope, the abnormal cells are well-differentiated and closely resemble healthy cells. Most grade 1 brain tumors have well-defined borders, making it easier for physicians to distinguish between the tumor and the surrounding healthy tissues.

Although grade 1 brain tumors are benign, they may still require treatment based on their location and potential impact on neurological functions. Treatment options may include surgical removal, especially if the tumor is causing symptoms or affecting critical areas of the brain. Regular monitoring and follow-up care are often recommended to track the behavior of the tumor over time.

Grade 2 brain tumors

Compared to grade 1 brain cancer, Grade 2 brain tumors grow slightly faster. When viewed under a microscope, the tumor cells appear moderately abnormal. Although less aggressive than higher-grade tumors, grade 2 brain tumors may have some infiltrative characteristics, can potentially spread to surrounding tissues and may recur after initial treatment.

The optimal treatment approach for a grade 2 brain tumor can vary based on its location and the overall health of the patient. Often, surgical removal of the tumor is the primary form of treatment. In some cases, radiation therapy may be recommended to target any remaining cancer cells after surgery or to treat an inoperable tumor. In certain situations, especially if the tumor is slow-growing and not causing significant symptoms, a physician may suggest close observation and periodic monitoring through imaging studies to track any changes in the tumor.

Grade 3 brain tumors

Compared to lower-grade brain cancer, grade 3 brain tumors have moderately to highly abnormal cells with an increased rate of growth and invasive characteristics. These tumors are considered malignant and have the potential to spread more aggressively into surrounding tissues.

Surgical removal of the tumor is a common initial step; however, complete removal may be challenging due to the invasive nature of grade 3 brain cancer. After surgery, or in cases where complete surgical removal is not feasible, radiation therapy and/or chemotherapy may be considered. Some grade 3 brain tumors respond favorably to targeted therapies, which are designed to home in on specific molecules or pathways involved in the growth of the cancer cells.

Grade 4 brain tumors

The most malignant and aggressive type of brain cancer, grade 4 brain tumors have highly abnormal cells that grow rapidly and exhibit invasive behavior, often infiltrating the surrounding brain tissues. Also known as glioblastomas, some grade 4 brain tumors produce their own blood vessels to support their rapid growth.

Treatment typically involves a combination of therapeutic approaches, including surgery, chemoradiation, tumor-treating fields (TTFields) and/or clinical trials. Due to the highly aggressive nature of grade 4 brain cancer, achieving a complete cure can be challenging.

Functional neurological status

In addition to a tumor grade, patients who are diagnosed with brain cancer are assigned a functional neurological status, which refers to the overall condition and performance of the CNS in managing bodily functions and activities. To determine a patient’s functional neurological status, a physician will evaluate the patient’s sensory and motor functions, cognitive abilities, reflexes and other neurological parameters.

New developments in brain tumor grading

Recently, the WHO released a new brain tumor classification and grading system that uses specific features to describe whether a tumor will grow slowly or quickly. These features include:

• An isocitrate dehydrogenase (IDH) mutation
• A high rate of cell division (mitotic index)
• Alterations in the CDKN2A/B genes
• A loss of chromosome 10
• A gain of chromosome 7
• A TERT promoter mutation
• An increased number of copies of the EGFR gene

Benefit from world-class care at Moffitt Cancer Center

The multispecialty team in Moffitt’s highly acclaimed Neuro-Oncology Program has the expertise necessary to effectively treat all grades of brain cancer, including rare and high-grade tumors. Complex cases are reviewed by our tumor board, providing our patients with the benefit of multiple expert opinions in one location.

You can request an appointment with a specialist in our Neuro-Oncology Program by calling 1-877-318-2560 or submitting a new patient registration form online. We do not require referrals.