One in 23 men and one in 25 women will be diagnosed with colorectal cancer in their lifetime. Many of these cancers start with a small growth called a polyp in the lining of their intestine.
Most polyps are harmless. But some can change over time and develop into colorectal cancer.
"Just because you have a colon polyp doesn't mean you have cancer, or that you will get cancer," says Dr. Monisha Singh, a gastrointestinal medical oncologist at Houston Methodist. "But this is the reason you get a colonoscopy — so we can find and remove polyps before they have the chance to become a problem."
Early detection and removal of colon polyps is crucial for colon cancer prevention.
What are colon polyps?
Colon polyps are growths of tissue that form on the inside lining of your colon or rectum. They develop when changes in certain genes cause cells to continue dividing even when new cells aren't needed.
Polyps can take a few shapes:
- Sessile – These appear as a raised bump or hill on the lining of the intestine
- Pedunculated – These look like a little ball of tissue at the end of a stalk, like a mushroom
- Depressed – These may look like a small dip in the lining of the intestine
Doctors classify polyps as neoplastic or non-neoplastic. Neoplastic polyps (adenomas, sessile serrated and traditional polyps) can become cancer. Non-neoplastic polyps (hyperplastic, hamartomas and inflammatory polyps) cannot.
Most colon polyps do not cause symptoms. If polyps do cause symptoms, they are most likely to include:
- Change in bowel habits – This could be constipation or diarrhea that lasts longer than a week
- Pain – A large polyp can block the intestine, leading to abdominal cramps
- Blood in your stool – This can show up as red streaks or make your poop appear black
By the time a person has symptoms, the polyp has likely already turned into cancer. This is why regular screening is so important. Make an appointment with your doctor if you experience these types of symptoms. (Related: 4 Colon Cancer Symptoms to Never Ignore)
How colon polyps become cancerous
Polyps initially develop when cells begin dividing more than normal. When cells divide quickly, it creates an environment in which mutations can occur — including cancer.
"You don't go from normal colon tissue to having invasive colon cancer overnight," says Dr. Singh. "It can take about 10 years for cancer to develop. That's why routine colon cancer screening — colonoscopy — is recommended every 10 years for someone at average risk of colon cancer."
The chance of a colon polyp becoming cancerous is about 8% to 10% over 10 years. The risk goes up to 24% over 20 years.
Not all polyps will turn into cancer. And not all of those that could turn into cancer will. But all polyps are considered "pre-cancerous" and should be taken seriously. Talk with your doctor to be sure you understand your risk and recommended screening options.
Who is more at risk of developing colon polyps or colon cancer?
Colon polyps are common. About 20% of adults overall and 40% over the age of 50 have them. Anyone can develop them, and you're more likely to develop them as you age. This is why it's recommended to start having colorectal cancer screenings at 45.
Most colon polyps are sporadic, which means they occur randomly through a genetic mutation. However, some genetic mutations are passed down through families, which increases a person's risk of developing colon polyps. Genetic disorders that can cause colon polyps include Lynch syndrome and familial adenomatous polyposis.
If you have one of these disorders or if you have had a parent, sibling or child who's had colon polyps, you may need more frequent and potentially earlier monitoring than people at average risk.
Some colon polyps may be partly triggered by environmental risk factors, such as your physical and social environment, health and lifestyle habits. Factors that could contribute to colon polyp development include:
- Diabetes
- Heavy alcohol use
- High-fat, low-fiber diet
- Inflammatory bowel disease
- Obesity
- Smoking
How to prevent and detect colon polyps
There's no way to prevent every colon polyp. But there are things you can do to reduce your risk of getting them:
- Eat whole foods and fewer animal fats
- Exercise regularly
- Avoid heavy drinking
- Don't smoke
(Related: How to Prevent Colon Cancer: 10 Ways to Reduce Your Risk)
The best way to find colon polyps is to have regular colonoscopies. During this procedure, which occurs under sedation and takes less than an hour, a healthcare provider will insert a long flexible tube with a light and a camera on the end into the colon. Before the procedure, you'll need to completely empty your bowels by drinking a gentle laxative preparation solution.
While some other tests — including blood, stool and imaging — can suggest the presence of colon polyps, colonoscopy is the only screening that allows health care providers to find and remove polyps at the same time.
Treatment options for colon polyps
When a colon polyp is found, it should be removed and tested for cancer, which is why colonoscopies are so effective. "We can remove the polyps on the spot, which is called polypectomy," adds Dr. Singh.
In rare cases when a polyp is in a challenging location or is too large to remove during the colonoscopy, you may need an additional minimally invasive endoscopic procedure. The endoscope will be inserted through the mouth or anus into the intestine. A saline solution is injected to create a blister around the polyp, which is then removed.
Some cases may require minimally invasive surgery during which an instrument called a laparoscope is inserted into the abdomen to remove the polyp.
Once a polyp is removed, it will be sent for testing to determine whether it is neoplastic or non-neoplastic. If a colonoscopy doesn't find any neoplastic polyps, and you don't have additional risk factors, you may not need another screening for 10 years. If you do have neoplastic polyps removed, your doctor may recommend you come back earlier.
"We know it's not fun to have a colonoscopy, and we realize there are barriers, such as doing the prep, having to take a day off work, finding someone to drive you and going under anesthesia," says Dr. Singh. "Polyps themselves are not cancer, but they have the potential to develop into cancer. We want to remove them before they have that chance."
(Related: Colorectal Cancer Screening: 4 Reasons You Shouldn't Put Off Your Colonoscopy)
