Benign and Malignant Brain Tumours – the difference

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

A “malignant” brain tumour looks very different under the microscope than the normal part of the brain where it started. The more unusual the tumour 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 tumour 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 tumour from growing back.

Understanding the jargon – the four Brain tumour grades

When you talk to your doctor and other medical staff about brain tumours, you may hear reference to the grade of a brain tumour.  In short (and really trying to avoid as much jargon as possible), the World Health Organization (WHO) has a classification system to define brain tumors.

This system collates brain tumors according to four grades, based on where the cells develop from and how the cells grow - from bengin tumours to the most aggressive malignant tumours. These grades are:

Grade I tumours: least malignant; generally grow at a slower rate and appear almost normal.

Grade II tumours: are relatively slow growing; appear slightly abnormal under the microscope;  can spread into nearby normal tissue and appear again.

Grade III tumours: malignant’; actively reproducing abornmal cells which grow into nearby brain tissue. These tumour tend to reappear, and can shift into Grade IV tumours.

Grade IV tumours: the majority of malignant tumours; fast to reproduce; have a very abnormal microscopic appearance and have dead cells at the centre; and easily grow into normal brain tissue nearby. These tumours generate new blood vessels in order to sustain their fast growth.

The most common example of Grade IV tumours are Glioblastoma multiforme and have to date, been the most common form of brain tumours in our membership.