What do the words "malignant" and "benign" mean?

A "malignant" brain tumor looks very different under the microscope than the normal part of the brain where it started. The more unusual the tumor cells look, the faster they usually divide and grow, and the more damaging they can be to normal areas of the brain. A malignant brain tumor grows into the normal areas of the brain so surgery cannot possibly remove all of it. Further treatment with chemotherapy and/or radiation is necessary to have the best chance of keeping the tumor from growing back.

"Benign" brain tumors usually look more like normal brain under the microscope. They usually grow and divide more slowly than malignant tumors. However, if their growth is not stopped, they can still cause a lot of damage. Some benign brain tumors can be treated with surgery alone, if the tumor is in an area where all the tumor can be removed without causing damage to important areas of the brain.

Answered by Dr. Regina Jakacki, pediatric oncologist, Children's Hospital of Pittsburgh

July, 2007