Diagnosis of Brain Tumors
The diagnosis and prognosis of brain tumors includes the following:
Review of Medical History
When you appear with symptoms suggesting a brain tumor, the first step will be a complete investigation of those symptoms and your overall health. You can prepare for this by keeping close track of your symptoms, when they first appeared, how often they happen, under what circumstances (sleeping, stressed, at work, at home), and if they seem to be changing. Since your brain and possibly your memory are involved, you would do well to write down this information and/or enlist the aid of a relative or friend. You might even ask the relative or friend to accompany you to your doctor’s appointment.
The doctor will perform a physical exam, paying particular attention to the neurologic exam. A neurologic exam uses several tests to evaluate muscle strength, coordination, reflexes, response to stimuli, the five senses, thought processes, and alertness. The doctor will also look into your eyes to check for signs of brain swelling.
Because it is far more common to have a cancer that spreads to the brain from somewhere else in the body, rather than starting in the brain itself, your doctor will also perform a complete physical examination and evaluate your lungs, breasts (if a woman), rectum, skin (looking for melanoma), or other structures deemed appropriate.
At this point, your doctor will either conduct further tests or refer you to a neurologist or neurosurgeon.
Further testing may include the following:
- CT scan – a type of x-ray that uses a computer to produce cross-sectional images of the inside of the body.
- MRI scan – a test that uses magnetic waves to produce images of the inside of the body. Using a large magnet, radio waves, and a computer, an MRI produces two-dimensional and three-dimensional pictures.
- Angiography – a dye is injected into an artery and a series of x-rays are taken. The dye coats the blood vessels, making it easier to see on the x-ray images if a tumor has invaded, compressed, or otherwise interfered with the normal functioning of blood vessels.
- Biopsy – the removal of a sample of brain tissue to test for cancer cells.
- Stereotaxis – use of a computer-assisted CT or MRI scan to locate the tumor and take a biopsy. To take a biopsy, the doctor drills a small hole in the skull, inserts a needle guided by stereotaxis (a method of identifying structures that can't be seen by using three-dimensional coordinates) and withdraws a sample of tumor tissue.
CT Scan of the Head
Sometimes tests are combined. For instance, certain contrast agents may be injected into the bloodstream that will produce better images with CT or MRI scanning, thus combining angiography with computerized imaging.
- Your doctor will want to evaluate your general health with a number of routine tests like blood and urine tests.
- If there is a suspicion that the brain tumor has metastasized from somewhere else in your body, a search for the primary site will also be done.
Cytology is the study of cells. The cytology of cancer cells differs significantly from normal cells, and physicians use the unique cellular features seen on biopsy samples to determine the diagnosis and assess the prognosis of a cancer. Nearly every tumor must be examined under a microscope to determine its type and characteristics. This requires obtaining a piece of the tumor, either with a needle carefully guided by some sort of medical imaging, or during open surgery (biopsy).
Gliomas (astrocytomas), in particular, come in a variety of grades, which predict the rate of tumor growth, its tendency to spread, its likely response to various forms of treatment, and the consequent survival prospects for the patient. Grading is therefore necessary in order to plan treatment. As with all cancers, there are certain appearances of brain cancer cells under the microscope that allow the pathologist to identify how aggressive (and consequently dangerous) a cancer is:
- The degree of difference between the cancer cell and its parent tissue
- The degree of variation from one cancer cell to another
- The speed at which the cancer is growing, measured by the number of cells that are actively dividing
- The density of cells in the tissue
- The presence of dead tissue, indicating that the cancer is growing faster than its blood supply
- The extent to which the cells are traversing their natural boundaries and invading adjacent tissues
Grading of Malignant Gliomas
Malignant gliomas are graded from I to IV. (Astrocytomas are the most common form of gliomas.)
Grade I – low-grade tumors. Grade I astrocytoma has a high cure rate with surgical removal. These grow slowly and generally stay localized in one area of the brain. They are the main type found in children.
Grades II and III – intermediate grade tumors. Grade III tumors are called anaplastic astrocytoma. These tumors have a prognosis that is worse than Grade I but better than Grade IV.
Grade IV – high-grade tumors. These tumors grow rapidly and can spread throughout the brain and spinal cord, and are even known to spread to structures beyond the nervous system, including lymph nodes in the neck. Aggressive treatment will be necessary. This is the most common type of astrocytoma found in adults. Grade IV tumors are called glioblastoma multiforme.
Grading deals with the microscopic appearance of the tumor itself. Staging adds to that information by identifying the tumor’s size and location, and how far it has spread.
Staging is the process by which physicians determine the prognosis of a cancer that has already been diagnosed. Staging is essential for making treatment decisions (e.g., surgery vs. chemotherapy). Several features of the cancer are used to arrive at a staging classification, the most common being the size of the original tumor, extent of local invasion, and spread to distant sites (metastasis). Low staging classifications (0 – 1) imply a favorable prognosis, whereas high staging classifications (4 – 5) imply an unfavorable prognosis.
Grading and staging taken together determine the prognosis and treatment. Of primary concern is the type of tumor—benign or malignant, indolent or aggressive—and where it originated. Both benign and malignant tumors are most commonly treated surgically. Every part of the brain is important. Therefore, the exact location and extent of the tumor must be determined beforehand, and surgery must be precisely planned so that the least amount of normal brain tissue is injured—none, if possible. Because of the importance of the brain tissue, in many cases surgery cannot be performed.
National Cancer Institute's Clinical Trials and Cancer Information
Harrison's Principles of Internal Medicine , 14th ed. McGraw-Hill; 1998.
Last reviewed February 2003 by Jondavid Pollock, MD, PhD
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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