What is the difference between a polyp and a tumor in the colon?

Different types: A polyp is a cluster of cells usually on a stalk representing transforming cells that may convert to Ca. A colon tumor is a area of bowel with malignant cells forming a discrete mass that can spread. Originally thought all Ca's of colon arose from polyps but now found that there is a transforming field effect in bowel where certain sites become polyps, not all converting and other sites, Cancer