Brain cancer is when cancer cells divide rapidly in the brain tissue. These cells grow to form a tumor that interferes with important brain functions. These tumors can either be malignant or benign. Benign tumors are noncancerous, because they can only grow locally. While malignant tumors are cancerous, because they can spread to other areas. Cancer cells that develop from brain tissue are called primary brain tumors, while tumors that spread from other regions of the body are called metastatic brain tumors. Brain tumors can be further categorized by their increasing growth rate: Grade I Grade II, Grade III, or Grade IV. Some of the most common symptoms include headaches, nausea and vomiting, changes in ability to talk, see, or hear, and problems with walking, balancing, thinking or memory. Brain cancer is diagnosed by MRI, CT scan, and biopsy tests and often treated with surgery, radiation therapy, and chemotherapy.