Diagnosing Metastatic Brain Tumors

A metastatic brain tumor is cancer that has spread to the brain from another part of the body. These tumors—which are also called brain metastases—are malignant, meaning they can spread throughout the body.

Any type of cancer can spread to the brain, but the most common ones are cancers of the lung, breast, kidney, and gastrointestinal tract, as well as melanoma.

Symptoms of brain metastases, which may develop gradually or rapidly, depend on the tumor’s size and location. They may include headache, weakness on one side of the body, seizures, vision changes, memory loss, or problems with balance and walking. A growing tumor often has fluid buildup, called edema, around it. Edema puts pressure on the brain and may damage the organ or be fatal.

To diagnose brain metastases, an NYU Langone doctor performs a physical exam and asks about your medical history. He or she also looks for symptoms associated with brain metastases. For example, the doctor may evaluate your mental status by asking a series of questions; check your reflexes, balance, and ability to move muscles; and conduct vision tests. Afterward, he or she may order one or more imaging tests.

MRI Scan

To determine if cancer has spread to the brain, a doctor may order an MRI scan—in which a magnetic field creates computerized two- or three-dimensional images—to better view the structure of the brain. You may receive an injection of a contrast agent, or dye, to enhance the image.

CT Scan

If a person is unable to have an MRI scan because he or she has a pacemaker or metal shrapnel in the brain, for instance, a doctor orders a CT scan. This test uses X-rays and a computer to create cross-sectional, three-dimensional images. The doctor may give you a contrast agent, or dye, by injection to enhance the image. Information from a CT scan helps the doctor decide whether surgery to remove the tumor can be performed.

PET Scan

A PET scan shows tumor activity using a small amount of radioactive glucose, or sugar, injected into a vein. This material collects in cancerous tissue and is detected with a special camera.

PET scans may be used after treatment for a brain metastasis to check for any remaining cancer.

Stereotactic Biopsy

If imaging tests suggest that a person has a brain tumor but cancer has not been diagnosed, a doctor may obtain a sample of the tissue using a technique called a stereotactic biopsy.

During this procedure, a doctor removes a small amount of tumor tissue using a probe directed by a three-dimensional computer navigation system. The doctor fixes a frame to your head prior to the test to keep it still during the procedure.

A computer system matches the MRI and CT images of the tumor to the person using the frame as the coordinate system. This allows a doctor to locate a tumor as well as the neighboring structures in the brain.

The doctor sends the tumor tissue to a laboratory for analysis. There, a pathologist examines it under a microscope to determine the type of metastasis a person may have. This helps your doctor create a treatment plan.