Brain Tumors

Biopsy

Mayo surgical pathologists provide instant tumor diagnosis, while the surgeon is operating.

A biopsy is usually required to definitely diagnose a brain tumor. The physician needs to know the tumor type and grade to plan the proper treatment. A biopsy involves removing a piece of the tumor for viewing under a microscope. At Mayo, the tissue is examined by a neuropathologist who specializes in examining brain and nervous system tumors. This is critical for an accurate diagnosis. Studies have shown that the diagnosis may change substantially for at least one-third of patients when pathological review is performed by an experienced neuropathologist as opposed to a general pathologist. Mayo's neuropathologists are internationally known for their expertise in diagnosing brain tumors.

Mayo Clinic patients also benefit from Mayo's use of rapid frozen tissue sections to analyze almost all tissue samples from the operating room. The frozen section method allows Mayo pathologists to almost instantly answer the critical questions of whether cancer is present, what kind is it and how far has it spread — and give the answers to surgeons while they are still operating, so they can remove the tumor as completely as possible in one operation.

A biopsy can be performed as part of surgery to remove a brain tumor, or separately. A stereotactic biopsy can be used for brain tumors in hard-to-reach areas. The surgeon drills a small hole into the skull, and, guided by the computer, inserts a thin needle to obtain the tissue. Computer-assisted brain surgery techniques used at Mayo allows biopsy specimens to be obtained from nearly any part of the brain, including the brainstem. Biopsy is generally performed only for patients with tumors in critical functional portions of the brain, where surgical removal (resection) would result in unacceptable neurologic injury.

Tumor Grades

Grading references how tumor cells look under the microscope. Grades 1 and 2 are low grade, Grade 3 is moderate and Grade 4 is high. Low grade means that the tumor cells resemble normal brain cells; they usually grow slowly and are not likely to spread. In high-grade tumors, the cells look very abnormal, and are more likely to grow quickly and spread.