Colon Polyps

Colon polyps are growths on the inside lining of your colon (large intestine). They’re a type of tumor, a cluster or mass of abnormal cells. Polyps are tumors that grow out of the mucous lining inside your hollow organs, like your gastrointestinal tract, your nose or female reproductive organs.

Colon polyps are common, and many are harmless. But some types can grow into cancer if they aren’t removed. This is why healthcare providers look for polyps in your colon during a colonoscopy, an exam inside your colon. While polyps aren’t cancer, almost all colorectal cancer starts from a polyp.

What are the different types of colon polyps?

Healthcare providers classify colon polyps in a couple of different ways. One way is by looking at the shape. If a polyp looks like a mushroom, with a “head” and “stalk,” they call it “pedunculated.” If it doesn’t have a stalk and looks more like a raised lump with a broad base, they call it “sessile.”

Providers also consider how polyps look under a microscope. Different types have different microscopic features because they grow and develop using different processes. These same processes also determine whether a polyp can grow into cancer or not. So, different types have different cancerous potential.

Types of colon polyps

Types of colon polyps include:

• Adenomatous polyps (adenomas).
  • Tubular adenomas.
  • Villous adenomas.
  • Tubulovillous adenomas.
• Serrated polyps.
  • Hyperplastic polyps.
  • Sessile serrated lesions.
  • Traditional serrated adenomas.
• Hamartomas (juvenile polyps).
• Inflammatory (pseudopolyps).

Neoplastic vs. non-neoplastic polyps

Healthcare providers classify colon polyps as neoplastic or non-neoplastic to indicate whether they can grow into cancer or not. Neoplastic polyps can grow into cancer. Non-neoplastic polyps can’t.

Neoplastic polyps include:

• All adenomatous polyps (adenomas).
• Sessile serrated lesions.
• Traditional serrated adenomas.

Non-neoplastic polyps include:

• Hyperplastic polyps.
• Juvenile polyps.
• Inflammatory pseudopolyps.

How common are colon polyps?

Colon polyps are common, especially as you get older. They affect about 20% of adults overall and about 40% over the age of 50, as well as 6% of children. People of all ethnicities and genders are at risk of colon polyps and colon cancer. They’re slightly more common in Western nations, in general.

What percentage of colon polyps are cancerous?

Most colon polyps have the potential to become cancerous, which is why healthcare providers remove them during a colonoscopy. But very few of them actually do turn into cancer, and it takes a long time for them to do so. Routine colonoscopies remove polyps before they have the chance to become cancer.

Around 75% of colorectal cancers start from adenomatous polyps, and about 80% of all colon polyps are adenomas. But only about 5% of adenomas are actually malignant. The risk of a random, average-size colon polyp becoming cancerous is estimated to be 8% over 10 years and 24% over 20 years.