Brain Tumors: Primary - Diagnosis

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Biopsy

A biopsy is a surgical procedure in which a small sample of tissue is taken from the suspected tumor and examined under a microscope for malignancy. The results of the biopsy also provide information on the cancer cell type.

In some cases, such as brain stem gliomas, a biopsy might be too hazardous because removing any healthy tissue from this area can affect vital functions. In such cases, diagnosis must rely on less invasive and possibly less accurate measures. Of promise is the stereotactic technique (also called stereotaxy), which uses computers to provide three-dimensional views of very small areas. This may allow precise biopsies of cancer cells without affecting healthy brain tissue. Expertise in this technique is extremely important, however, and the technique is not widely available.

Determining a Prognosis

The survival rates in people with brain tumors depend on many different variables:

• Whether the tumor is malignant or benign
• Cancer cell type and location (location affects whether the tumor can be removed surgically or not)
• The tendency to spread and the growth rate (tumor grade)
• Patient's age
• Patient's ability to function
• Duration of symptoms

The outlook is poorer in the very youngest and very oldest patients, although younger patients who survive 2 years after diagnosis have a much better outlook than older patients.

Grading Tumors. Malignant primary brain tumors are classified according to tumor grade. Grade I is the least cancerous, and Grades IV and V are the most dangerous. Grading a tumor attempts to predict its tendency to spread and its growth rate. It is based on the appearance of the tumor cells as seen under a microscope.

• Lower-grade (I and II) tumor cells are well defined and almost normal-shaped. (Some primary low-grade brain tumors are curable by surgery alone, and some are curable by surgery and radiotherapy. Low-grade tumors tend to have the most favorable survival rates and high-grade the least. However, this is not always the case. For example, some low-grade II gliomas are at very high risk for progression.)
• Higher-grade (III and IV) tumor cells are abnormally shaped and are more diffuse, which indicates more aggressive behavior. (High-grade brain tumors usually require surgery, radiotherapy, chemotherapy, and possibly investigational treatments.)
• In tumors that contain a mixture of different-grade cells, the tumor is graded using the highest-grade cells in the mixture, even when there are very few of them.