Understanding Colorectal Cancer: What Is Colorectal Cancer?


To understand colorectal cancer, it’s first important to understand what cancer is: basically, the production of abnormal cells.

The body is programmed to routinely replenish cells in different organs. As normal cells age or get damaged, they die off. New cells take their place. This is what’s supposed to happen. Abnormal cell growth refers to a buildup of extra cells. This happens when:

  • New cells form even though the body doesn’t need them or
  • Old, damaged cells don’t die off.
  • These extra cells accumulate to form a tissue mass, lump, or growth called a tumor. These abnormal cells can destroy normal body tissue and spread through the bloodstream and lymphatic system.

Colorectal cancer is one of the most common cancers in the U.S. today. 90-95% of all colorectal cancers are adenocarcinomas. This is a cancer that begins in cells that make and secrete fluids such as mucus. These cells are in glandular tissue.

To better understand what an adenocarcinoma is, consider the word: Adeno means gland; Carcinoma is a malignant tumor.

Although these tumors are malignant, they all generally start from adenomas. Adenomas are pre-cancerous growths called polyps. The bigger the adenoma is, the more likely it is to become cancerous.

Colon polyps are a common occurrence. In fact, 25% of people over age 50 have polyps.

Benign vs. Malignant: What’s the Difference?

Benign means not cancerous. A benign tumor can get larger but does not spread to other tissues or organs.

Malignant means cancerous. A malignant tumor’s cells can invade nearby tissue and lymph nodes and then spread to other organs. These cells are destructive.

Benign tumors

Can be removed

Usually don't grow back

Are rarely fatal

Don't spread to other tissues or body parts

Malignant tumors

Can often be removed

Sometimes grow back

Can invade other tissues and organs and cause damage

Can spread to other body parts

Can be fatal



Next: How is colorectal cancer diagnosed? 

Back to “Understanding Colorectal Cancer: An Introduction”