Brain Cancer (cont.)
What Exams and Tests Diagnose Brain Cancer?
If findings of a medical history and physical examination suggest to the health-care professional that a person may have a problem in the brain or brain stem, additional tests may be done.
- Many people will have a CT scan of the brain, especially if the person is seen emergently.
- This test is like an X-ray but shows more detail in three dimensions.
- Usually, a dye, referred to as a contrast material, is injected into the bloodstream to highlight abnormalities on the scan.
People with brain cancer often have other medical problems; therefore, routine laboratory tests may be performed.
- These include analysis of blood, electrolytes, liver function tests, and a blood coagulation (clotting) profile.
- If the person has mental-status change as the main symptom, blood or urine tests may be done to rule out drug use as a cause of such symptoms.
The standard way of evaluating the nature and extent of a brain tumor is an MRI scan (note that some hospitals do not have MRI scanners).
- This is because MRI has a higher sensitivity for detecting the presence and characteristics of a tumor. Specifically, the relationship of the tumor to the surrounding brain, the brain coverings, cerebrospinal fluid spaces, and vascular structures is assessed to come up with a provisional diagnosis of the nature of the tumor.
- Currently, however, many institutions that do have MRI scanners still use the CT scan as a screening test for tumors.
If CT or MRI scans indicate the presence of a brain tumor, the person will be referred to brain surgery (a neurosurgeon). If one is available in the area, the person may also be referred to a specialist in radiation therapy called a radiation oncologist, and a medical oncologist if they specialize in the chemotherapeutic treatment of brain tumors (a medical or neuro-oncologist).
The next step in diagnosis is confirmation that the person has cancer in the brain. A scan can be considered to be highly suspicious, or even highly likely to demonstrate a brain tumor, but confirmation requires a tissue diagnosis whenever possible. A small sample of the tumor (a biopsy) is taken to identify the type of tumor and the grade of the tumor.
- The most widely used technique for obtaining a biopsy is a surgical procedure called a craniotomy. The skull is opened, usually with the intention of removing the whole tumor if possible. A biopsy is then taken from the tumor.
- If the surgeon is unable to remove the entire tumor, a small piece of the tumor is removed.
- In some cases, it is possible to collect a biopsy without opening the skull. The exact location of the tumor in the brain is determined stereotactically, that is, by using CT or MRI scans while the head is held still in a frame. A small hole is then made in the skull and a needle guided through the hole to the tumor. The needle collects the biopsy and is removed. This technique is called stereotaxis, or stereotactic biopsy. This process does not treat the tumor and is generally reserved for situations in which the tumor is either inaccessible or is thought to be sensitive to radiation therapy (such as CNS lymphoma or pineal germ cell tumor) and surgery is not necessary to adequately treat the patient.
- The biopsy is examined under a microscope by a pathologist (a physician who specializes in diagnosing diseases by looking at cells and tissues) and usually assigned a NCI grade.
Medically Reviewed by a Doctor on 9/11/2017
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