Brain Tumor Diagnosis

If you have a brain tumor, it is important to get the most accurate diagnosis possible. This will help your doctor pinpoint the exact type of tumor, helping them to give you the most effective treatments while limiting side effects.

At MD Anderson, we have the most modern and accurate equipment available to identify brain tumors and find out exactly how far they may have spread. We also have a team of expert neuropathologists, doctors who focus exclusively on diagnosing brain and spine tumors.

If you have symptoms that may signal a brain tumor, your doctor will examine you and ask you questions about your health, your lifestyle and your family history.

One or more of the following tests may be used to find out if you have a brain tumor and if it has spread. These tests also may be used to find out if treatment is working.

Imaging tests

Imaging exams look for where cancer is inside the body. Imaging exams for brain tumors may include:

• CT (computed tomography) scans
• MRI (magnetic resonance imaging)

Biopsy

While imaging tests may show an area where there may be a brain tumor, doctors need a tissue sample to definitively diagnose a primary brain tumor. Tissue samples are retrieved through a biopsy. Most of the time, doctors remove the entire tumor through surgery. In some cases, a small tissue sample is removed with a needle. The tumor tissue is then examined under a microscope. It also undergoes advanced molecular testing to determine the exact tumor type. Your neurosurgeon will determine which type of biopsy is best for your tumor.

Lumbar puncture

A small amount of cerebrospinal fluid (clear liquid in and around the brain and spine) is removed with a needle and examined under a microscope. This test may be done if doctors suspect a tumor has spread to the layers of tissue that cover the brain (the meninges) and into the spinal fluid.

Molecular diagnosis

Different cancers have different features on the molecular level. A molecular diagnosis identifies the features that can impact treatment and prognosis. This information helps doctors create the most effective treatment plan for each patient.

Genetic testing

Some genetic mutations can increase the risk of developing certain diseases. Brain cancer patients may undergo genetic testing to help doctors better understand the cancer and design the best plan to treat it.

Brain Tumor Grading

Many cancers are assigned a stage, which describes how much cancer is in the body and where it has spread. Primary brain tumors typically do not spread to other parts of the body, so they are not staged.

Instead, most brain tumors are graded on a scale developed by the World Health Organization. Tumor grading classifies tumor cells by how abnormal they look under the microscope, how quickly the tumor is dividing, and what molecular characteristics are present. Grade 1 tumors are the least aggressive, while grade 4 tumors are the most aggressive.

Brain tumors can start out at a low grade and over time become more aggressive and transform into high grade tumors. They can also start as a high-grade brain tumor without ever being a low-grade tumor. 

Brain tumor grades include: 

• Grade 1 (low-grade) — The tumor cells look more like normal cells under a microscope and grow and spread more slowly than grade 2, 3, and 4 tumor cells. They rarely spread into nearby tissues. Grade 1 brain tumors may be completely removed by surgery.
• Grade 2 — The tumor cells grow and spread more slowly than grade 3 and 4 tumor cells. They may spread into nearby tissue and may recur (come back). Some tumors may become a higher-grade tumor.
• Grade 3 — The tumor cells look very different from normal cells under a microscope and grow more quickly than grade 1 and 2 tumor cells. They are likely to spread into nearby tissue.
• Grade 4 (high-grade) — The tumor cells do not look like normal cells under a microscope and grow and spread very quickly. There may be areas of dead cells in the tumor. Grade 4 tumors usually cannot be completely removed by surgery.