Colorectal cancer often takes many years to grow, and nearly all cases of colon cancer and rectal cancer start off as a polyp. Here’s everything you need to know about colon polyps and rectal polyps.
What Are Colorectal Polyps?
A polyp is a group of cells that grow together, and a colon polyp occurs when these cells grow on the inside of the colon or rectum. There are a few different shapes of polyps.
Some polyps grow on the end of a stalk and look similar to a mushroom (this is called a pedunculated polyp). Adenomas are polyps that grow like a mushroom with a stalk.
Sessile (or Flat) Polyps
Sessile polyps grow without the narrow stalk and seem to lie flat against the wall of the colon. These polyps are also known as flat polyps. Sessile only means that they don’t have a narrow stalk. It’s possible for a large, protruding polyp to have a sessile base.
Cancerous and Precancerous Polyps
Both pedunculated and sessile polyps can turn into benign (non-cancerous), precancerous and cancerous polyps. It’s important to know your polyp type – such as hyperplastic, inflammatory, hamartomatous, adenomatous, hyperplastic and sessile serrated polyps – to know your cancer risk.
Keep reading to learn about your risks with these types of colon polyps!
Colon Polyp and Rectal Polyp Symptoms
It’s hard to know if you have polyps because they don’t usually cause symptoms until they develop into cancer. This is why screening is important!
Screening for colorectal cancer = screening for polyps.
Most polyps can be safely removed during a colonoscopy, thus removing the risk of the polyp growing into cancer.
Most of the time, polyps don’t come with any symptoms. However, for some, polyps bleed. Bleeding may be intermittent. It is always important to notify your doctor if you notice blood in your stool.
Talk to your doctor if you experience rectal bleeding, a change in bowel habits, pain, and anemia. This could mean you have a polyp and you need to be screened, or that you need additional surveillance. Learn more about the symptoms of colorectal cancer.
Types of Polyps and Cancer Risk
Just because you have a polyp, that doesn’t mean it’s cancer (also called a malignant tumor). Some polyps grow into cancer, but others may not.
Does the Size of a Polyp Impact Cancer Risk?
Your cancer risk does increase with the size of the colon polyp, but there is no specific, generalized size that indicates a polyp is becoming cancerous.
However, one centimeter is the cutoff between an “advanced” and “non-advanced” polyp.
If you grow an advanced polyp, your doctor will likely ask you to return for a follow up sooner than normal. Not all polyps will become cancerous, but it is important to remove them all to block the possibility.
What Types of Colon Polyps Probably Won’t Become Cancer?
Most likely, these polyp types won’t become cancer:
These colon polyps are often seen with ulcerative colitis or Crohn’s disease, inflammatory bowel diseases (IBD). Although the polyps are generally non-cancerous, if you have IBD, you are at increased risk of colorectal cancer.
Hamartomatous polyps are generally noncancerous, unless they are found in people with a polyposis syndrome like Peutz Jaeghers, Cowden’s, or Juvenille Polyposis, in which case they are associated with the development of colorectal cancer. Learn more about genetic syndromes.
What Types of Polyps Likely Will Become Cancer?
These types of polyps come with a cancer risk.
Adenomatous Polyps (Adenomas)
These polyps are a big deal! Approximately two-thirds of colon polyps are adenomas – that means 66 percent of all colon polyps are precancerous!
Adenomas are described by growth patterns, or microscopic descriptions a pathologist makes to determine how often you need to return for a colonoscopy.
- Tubular growth pattern – generally applies to smaller adenomas growing in a tube shape, less than half an inch in size
- Villous growth pattern – generally applies to larger adenomas growing in a shaggy, cauliflower-like shape
- Tubularvillous – adenoma with a mixture of both tubular and villous growth patterns
If you’ve had an adenoma in the past, you are likely to develop new polyps, and you may need to be screened more often. It’s also very important to tell your family if you’ve had adenomatous polyps.
If a hyperplastic polyp is found on the right side of your colon, some research suggests the polyp could become cancerous. However, if not linked to a hereditary syndrome, hyperplastic polyps generally do not carry a cancer risk.
Sessile-Serrated and Traditional-Serrated Polyps
Histologically, these polyps appear with a “saw tooth” (serrated) border of their glands, and they are considered precancerous polyps.
How Long Does it Take a Polyp to Turn into Cancer?
The general theory is that it takes about 10 years for an adenoma (precancerous polyp) to turn into cancer.
This varies for those with a hereditary syndrome (people who often see polyps and cancer at an earlier age).
What is Dysplasia?
Dysplasia describes how histologically advanced your polyp is, and all adenomas are dysplastic. Pathologists use the term “high-grade dysplasia” to distinguish polyps with more advanced histology – or polyps that appear more worrisome for cancer.
Colorectal Polyp Causes
Anyone can grow a polyp, and colon polyps are common. Can you do anything to prevent polyps? Yes and no. Your risk of developing a polyp increases with age, which you cannot control, as well as if you have personal or family history of polyps and/or colorectal cancer. However, your risk of colon polyps also increases if you smoke and/or if you are overweight. It is important to follow a healthy lifestyle to reduce your risk of polyps and cancer.
Colorectal Polyps FAQ
Answers to the most common questions we receive about colon and rectal polyps, such as:
- How do I know if I have polyps in my colon or rectum?
- What if polyps are found during a colonoscopy?
- Are polyps hereditary?
- What if I have a cancerous polyp?
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