Colon cancer is a term that is used for cancer that originates in the colon. It could also be referred to as colorectal cancer because cancer of the colon and cancer of the rectum have many features in common.
Most colon cancer develops over time. A growth of abnormal tissue, called a polyp, forms on the lining of the colon. These usually start as non-cancerous (benign) polyps, but over time some change to be malignant, or cancerous. There are two types of polyps:
- Adenomatous polyps – polyps that can change into cancer, a pre-cancerous condition
- Hyperplastic polyps and inflammatory polyps – polyps that are non-cancerous
Many physicians believe that hyperplastic polyps could turn into pre-cancerous polyps or that those who have hyperplastic polyps have a greater risk of developing adenomatous polyps, especially when they are found in the ascending colon.
Types of Colon Cancer
Adenocarcinomas – The most common colorectal cancer. Starts from cells that form glands that make mucus to lubricate the inside of the colon and rectum.
Carcinoid tumors – Start from specialized hormone-producing cells in the intestine
Gastrointestinal stromal tumors (GISTs) – Start from specialized cells in the wall of the colon. They can be found anywhere in the digestive tract, but usually in the colon.
Lymphomas – Cancers of the immune system cells that start in the lymph nodes but could also start in the colon, rectum or other organs.
Sarcomas – A rare type of tumor that starts in blood vessels or in muscle and connective tissue in the wall of the colon and rectum.
How it spreads
Polyps can eventually grow into the walls of the colon and possibly into the blood vessels or lymph vessels. These lymph vessels drain into the lymph nodes that contain immune cells that help fight off infections. Infected lymph nodes travel through your body containing the cancerous cells spreading the cancer.