A tumor is classified as benign when it's unlikely to spread & as this when it's cancerous
... Also, 
some benign tumours that arise from cells in hormone glands can make too .... a 
cancer is classified depending on its type (grading) and how far it has spread in 
the... [DOC] [TLE] Benign brain tumour - NHS Choices [PAR] A benign (non-cancerous) brain tumour is a mass of cells that grows slowly in ... 
be slow-growing and unlikely to spread, so they're usually classed as benign.