human
I have a friend who has just been diagnosed with a brain tumor. What is a brain tumor and what are the different types?
assistant
A brain tumor is a mass of abnormal cells that can form in the brain. There are many different types of tumors, but they all start from normal cells that grow out of control and invade other parts of the brain. Brain tumors can be benign (not cancerous) or malignant (cancerous). The most common type of brain tumor is called a glioma, which is a type of malignant tumor.