Diagnosing brain cancer

This page was reviewed under our medical and editorial policy by

Maurie Markman, MD, President, Medicine & Science

This page was updated on June 8, 2022.

The chance of developing a cancerous brain or spinal cord tumor is about 1 percent across a person’s lifetime. In 2024, about 25,400 people will be diagnosed with malignant spinal or brain tumors (14,420 males and 10,980 females), according to the American Cancer Society (ACS). This number includes both children and adults.

A thorough and accurate diagnosis is the first step in developing a brain cancer treatment plan. A multidisciplinary team of experts uses a variety of tests and tools for diagnosing brain cancer, evaluating the disease and customizing a treatment plan based on each individual patient’s disease and situation.

The patient’s care team will likely consist of a:

  • Gastroenterologist, a doctor who specializes in the diagnosis and treatment of digestive tract diseases
  • Medical oncologist, a doctor who specializes in the diagnosis and treatment of cancer via chemotherapy, immunotherapy and targeted therapy
  • Radiation oncologist, a doctor trained in using radiation therapy to treat cancer
  • Surgical oncologist, a doctor who treats cancer surgically

Throughout treatment, imaging tests track the size of the tumor(s) and monitor response to treatment, so the treatment plan may be modified as needed.

Tests for brain cancer diagnosis

Neurological exam

During the brain cancer diagnosis process, the care team will start by performing a neurological examination. During this test, the patient’s reflexes, balance, vision and hearing will be evaluated, among other factors.


Whenever possible, a full surgical resection of the cancerous tissue is performed. If such a resection threatens neurological function, a lesser resection, or simple biopsy, is performed.

A biopsy for brain cancer involves the removal of a small amount of the cancerous brain tissue. This helps evaluate the tumor in order to develop a treatment plan. A needle biopsy may be performed for tumors in difficult-to-reach or critical areas of the brain.

Tumor markers

The main lab test for brain cancer is advanced genomic testing, which analyzes a tumor’s genomic profile, also referred to as a tumor marker, to look for DNA alterations that may be causing the cancer to grow. By identifying the mutations (changes) in a cancer cell's genome, doctors may better understand the tumor’s behavior and tailor treatment based on these findings. Several tumor markers may be evaluated during the brain cancer diagnosis process:

  • 1p/19q co-deletion: When the p-arm of chromosome 1 and the q-arm of chromosome 19 are missing, it’s referred to as a 1p/19q co-deletion. The care team may look for this tumor marker to help guide treatment decisions, particularly for patients with anaplastic oligodendroglioma.
  • IDH mutation: When a mutation is found in the isocitrate dehydrogenase gene of patients with glioma tumors, it may help the care team evaluate the patient’s prognosis.
  • MGMT changes: When the methyl guanine methyl transferase gene has changed, the care team is able to better evaluate the patient’s glioblastoma prognosis.

Nuclear medicine bone scan

By capturing images of bones on a computer, a nuclear medicine bone scan may reveal whether the brain cancer has spread to the bone. To perform the scan, a small dose of radioactive material is injected into a blood vessel, where it travels through the bloodstream, gathers in the bones, and is detected by a scanner through nuclear imaging.


This procedure uses X-rays to obtain multiple, detailed, images of the blood vessels in the brain. An angiography may be used to plan the surgical resection of a tumor near an area of the brain with many blood vessels. Sometimes, this test is used to embolize (close off) blood vessels feeding a tumor prior to surgery.

Other imaging tests to diagnose brain cancer

Imaging tests for brain cancer produce pictures of the brain to determine the location and grade of brain tumors. A contrast agent may be used to distinguish normal and abnormal brain tissue.

Imaging tests used in brain cancer diagnosis include:

MRI (magnetic resonance imaging): MRIs are used to look for brain and spinal cord tumors because they tend to provide greater detail than CT scans. However, for the bones and skull, MRI does not provide the same image quality as CT scans and, therefore, may not show the effects of tumors on the skull. MRA is commonly used to evaluate the vasculature of the brain by allowing three- dimensional evaluation.

CT (computed tomography) scan: CT scans create detailed images of the body’s soft tissues and may be performed when MRI is not an option, such as with overweight or claustrophobic patients. CT scans also show greater detail of bone structures near the tumor. CTA is commonly used to evaluate the vasculature of the brain by allowing three-dimensional evaluation of the blood vessels.

PET (positron emission tomography) scan: PET scans may be used for fast-growing, high-grade tumors. Following treatment, a PET scan may be performed to determine whether tumor tissue remains.

Brain cancer blood tests

No specific blood tests are available to definitively diagnose brain cancer or a brain tumor. However, blood tests are used at diagnosis and throughout brain cancer treatment to evaluate the patient’s overall health and confirm whether other organs are functioning properly.

Next topic: How is brain cancer treated?

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