https://www.webmd.com/colorectal-cancer/guide/colorectal-polyps-cancer

"Nearly all colon and rectal cancers begin as a polyp, a growth on the inner surface of your colon. Polyps themselves usually aren’t cancer."

"How Can I Prevent Colon Polyps?

Healthy habits can lower your odds of having colon polyps. For example, you should:

• Eat a diet with lots of fruits, vegetables, and fiber-rich foods like beans, lentils, peas, and high-fiber cereal.
• Lose weight if you’re overweight.
• Limit red meat, processed meats, and foods that are high in fat.
• Talk to your doctor about whether calcium and vitamin D supplements are right for you. Some studies suggest they could lower your odds of colon cancer, but others don't.
• If you have a family history of colon polyps, ask your doctor if you should get genetic counseling and when you should start screening for polyps.
• Talk to your doctor about taking aspirin regularly. There is some evidence that aspirin has a preventive effect against colon cancer.
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Types of Colorectal Cancer

There are several types of colorectal cancer, based on where it starts.

• Adenocarcinoma. This is the most common kind, making up 96% of cases. It starts in cells that make mucus for your colon and rectum.
• Carcinoid tumor. This begins in cells that make hormones.
• Gastrointestinal stromal tumor. This forms in cells in the wall of your colon that tell your gastrointestinal muscles to move food or liquid along.
• Lymphoma. This is cancer of your immune system cells.
• Sarcoma. This starts in connective tissues like blood vessels or muscle layers."