A tumor is classified as benign when it's unlikely to spread & as this when it's cancerous
[DOC] [TLE] Brain Tumor facts, information, pictures | Encyclopedia.com articles ... [PAR] A brain tumor is considered malignant if it contains cancer cells, or if it is ... 
Benign brain tumors do not infiltrate nearby tissues but can cause severe pain, ... 
and how likely it is to invade other tissues; how closely its cells resemble normal 
cells.