brain tumors diagnosed and staged

How are brain tumors diagnosed and staged?

When a patient presents with symptoms suggestive of a brain tumor, the physician will perform a thorough history and physical examination. After that, the key to making the diagnosis is appropriate radiology imaging.

Imaging can be performed with either a CT scan or MRI scan. A CT scan is a three dimensional x-ray, and patients will often be injected with a contrast agent to help visualize any abnormalities. CT scans are good tests because they are quick and easy to obtain, and will often be used as the first step towards making a diagnosis. However, an MRI scan is a better test for evaluating abnormalities in the brain. MRI scans utilize powerful magnets to make a three-dimensional picture. An MRI picks up finer detail than a CT scan, and is the study of choice to make the diagnosis of a brain tumor. MRI scans are usually obtained with the use of an injectable contrast agent as well.

There are some further imaging studies that may be used to determine if a mass in the brain is a tumor (as opposed to other causes, such as infection) and if it is a tumor, what type it is. There is a special type of MRI, known as MR spectroscopy or MRS, which allows your physician to learn more about the contents of the mass and helps them determine what the mass is. A functional MRI is another special type of MRI that can help define areas of the brain, which activate when a person moves or speaks. This allows the doctor to “map the brain” and helps the doctor know which areas to avoid during surgery if the tumor is close to a portion of the brain, which is critical for movement or speech.

For many types of brain tumors, the imaging characteristics are distinctive enough to give physicians a pretty good idea of the diagnosis. The primary management of most brain tumors is surgery. If imaging reveals that a mass suspicious for a brain tumor is in a surgically accessible spot, the patient is generally scheduled for surgery without any further diagnostic testing. After surgery, the specimen can be examined under the microscope by a pathologist, and a final diagnosis can be made. However, sometimes, tumors are not in a safe location for surgery. In those cases, in order to make a diagnosis, patients will often need a biopsy. A biopsy is a procedure where a small piece of the tumor is obtained using a needle under image guidance. The biopsy is usually done as a stereotactic biopsy, where the head is immobilized with a frame that is attached to the skull with pins. A scan of the brain is then done with the frame in place. With the same immobilization device on, the person is taken to surgery and the surgeon can use the scan to guide them precisely to the tumor.

Occasionally, your physician may need to examine the fluid that surrounds the brain and spinal cord (cerebrospinal fluid or CSF for short) to see if there are any cancer cells that have spread to this liquid. This can be done with a procedure known as a lumbar puncture, or an LP for short. A needle is inserted between the vertebral bodies (bones of the spinal cord) and into the sack that holds the spinal cord. Some of the CSF is taken out and a pathologist can examine it and determine if there are cancer cells present.

If it is thought that the brain tumor is a metastasis (spread from another area), radiologic imaging may be performed of others areas of the body to locate the primary tumor (where the tumor originated). This can be done with an X-ray or a CT scan. Your physician may also order other laboratory tests to determine if cancer is affecting other organs.

Primary brain tumors do not have a classic staging system the way most other cancers do. This is because the size of a brain tumor is less important than its location and the type of brain cell that makes it up. The likelihood of curing a brain tumor has to do with its location, the cell that makes it up, and how the tumor cells look under a microscope. Your doctor will give you a sense of how dangerous your tumor is and how it should be treated after weighing these factors.

Brain metastases are considered within the staging system of the cancer from which they originated. Thus, the presence of brain metastases automatically makes the primary tumor a stage IV cancer, because stage IV means the presence of any metastasis. For example, a lung cancer that has spread to the brain is a stage IV lung cancer.