A colon polyp is a small clump of cells that forms on the lining of the colon. Most colon polyps are harmless. But over time, some colon polyps can turn into colorectal cancer. Colorectal cancer can be deadly when found in its later stages.

The most common type of precancerous polyp is an adenomatous polyp, often called an adenoma. Because adenomas are the polyps that most often change into colorectal cancer, healthcare professionals recommend removing them to prevent them from growing larger or becoming cancerous.

Anyone can develop colon polyps, and your risk increases as you age. Your risk of colorectal cancer also is higher if you are overweight, smoke, have a personal history of colon polyps, or have a family history of advanced colon polyps or colorectal cancer.

Colon polyps don't usually cause symptoms. It's important to have regular screening tests because colon polyps found early can usually be taken out safely and completely. The best prevention for colorectal cancer is regular screening.

Types

Medical professionals classify colon polyps into two groups, nonneoplastic and neoplastic. Nonneoplastic polyps are generally harmless and rarely turn into cancer. Neoplastic polyps are considered precancerous, which means they can turn into cancer if they are not taken out.

Noncancerous polyps

Nonneoplastic polyps are generally considered harmless. They include:

• Hyperplastic polyps. These are very common, especially in the lower colon and rectum. They are usually small and almost never turn into cancer.
• Inflammatory polyps. These polyps often occur in people with inflammatory bowel disease such as Crohn's disease or ulcerative colitis. These polyps also are called pseudopolyps. The polyps themselves do not turn into cancer, but they indicate long-term inflammation in the colon, which raises overall cancer risk.
• Hamartomatous polyps. These polyps are made of regular tissue that grows in a way that's not organized. In a child, a single polyp is usually harmless and often goes away on its own. However, when many are present, as in juvenile polyposis syndrome, cancer risk increases. Peutz-Jeghers polyps are another type that appear in a rare genetic syndrome and are linked to higher cancer risk. PTEN-hamartoma polyps, seen in Cowden syndrome, also can raise cancer risk.

Precancerous polyps

Neoplastic polyps are more likely to become cancerous. They include:

• Adenomas, also called adenomatous polyps. These are the most common neoplastic polyps. They include:
  • Tubular adenomas. These are the most common type and usually have the lowest risk of becoming cancer.
  • Tubulovillous adenomas. These polyps combine features of tubular and villous adenomas and carry a higher risk.
  • Villous adenomas. These are the least common but the most likely to turn into cancer, especially when large.
• Serrated polyps. These polyps follow a distinct pathway to cancer. They include:
  • Sessile serrated lesions (SSLs). SSLs are flat polyps often found in the right colon. They can be difficult to detect during colonoscopy and may change into cancer, especially if they are large or show irregular cell growth. SSLs are sometimes called sessile serrated polyps (SSPs) or sessile serrated adenomas (SSAs).
  • Traditional serrated adenomas (TSAs). TSAs are rare and usually located in the left colon. These are clearly precancerous and are always removed when found.

Most people with colon polyps do not have any symptoms, which is why screening tests are so important. Colon polyps are often found as a part of routine colorectal cancer screening.

Symptoms that should prompt an appointment with a healthcare professional include:

• Changes in bowel habits. Constipation or diarrhea that lasts longer than a week may mean the presence of a larger colon polyp or cancer. However, several other conditions also can cause changes in bowel habits.
• Changes in stool color. Blood can show up as red streaks in the stool or make stool appear black. A change in color also may be caused by certain foods, medicines or dietary supplements.
• Mucus in stool. Stool often contains a small amount of mucus. Mucus is a jellylike substance that your intestines make to keep the lining of your colon moist and lubricated. But you should talk with a healthcare professional if you notice an increased amount of mucus in stool. Mucus by itself usually isn't a reason to do medical tests, but it's helpful to know if you see it along with other symptoms.
• Iron deficiency anemia. Bleeding from polyps can happen slowly over time, without visible blood in the stool. Chronic bleeding may lead to iron deficiency anemia, which can cause tiredness and shortness of breath.
• Pain. A large colon polyp or cancer can block part of the bowel, leading to cramping and belly pain.
• Rectal bleeding. This can be a sign of colon polyps, cancer or other conditions, such as hemorrhoids or minor tears of the anus.

When to see a doctor

See a healthcare professional if you have:

• Belly pain.
• Blood in the stool.
• A change in bowel habits that lasts longer than a week.
• Weight loss that happens without trying.

You should be screened regularly for colorectal cancer if:

• You're age 45 or older.
• You're younger than age 45 and you have medical conditions or family history that increases your risk of colorectal cancer.

Experts haven't found a single cause for colon polyps. They form when the usual process of cell growth and repair in the colon goes off track. Instead of replacing old cells in an orderly way, the body makes extra cells, which build up and form a polyp on the smooth lining of the intestine. Polyps can grow anywhere in the large intestine, including in the colon and rectum.

When polyps grow in the rectum, they are called rectal polyps. The rectum is the lower part of the colon, so rectal polyps are simply a type of colon polyp.

Aside from being classified by where they grow, colon polyps also are classified by their type. Noncancerous, also called nonneoplastic, polyps usually do not become cancer. Precancerous, also called neoplastic, polyps include adenomas and serrated lesions. Most colorectal cancers begin in an adenoma or serrated lesion that has been present for many years. In general, the larger the precancerous polyp, the greater the risk that it will become cancerous.

Factors that might increase the risk of colon polyps or cancer include:

• Age. Most people with colon polyps are 45 or older.
• Having certain intestinal conditions. Having inflammatory bowel disease, such as ulcerative colitis or Crohn's disease, raises the overall risk of colorectal cancer.
• Family history. Having a parent, sibling or child with advanced colon polyps increases the risk of getting them. An example of an advanced colon polyp is one that is 10 mm in diameter or larger. If many family members have them, the risk is even greater.
• Personal history of colorectal polyps. Previous polyps are a risk factor for forming new polyps.
• Smoking and excess alcohol use. Studies show that people who have three or more alcoholic drinks a day have an increased risk of getting colon polyps. Alcohol intake combined with smoking also appears to increase the risk.
• Having diabetes. Diabetes increases polyp risk by 50% among all age groups.
• Obesity, lack of exercise and a less healthy diet. The risk of colon polyps increases for people who are overweight, don't exercise regularly and eat a less healthy diet.
• Race. In the U.S., Black people have a higher risk of developing colorectal cancer.

Polyp syndromes

Hereditary conditions are health concerns passed down from parents. Rarely, people inherit gene changes that cause colon polyps to form and increase the risk of colorectal cancer. Screening and early detection can help prevent the growth or spread of these cancers.

Conditions that cause colon polyps include:

• Lynch syndrome, also called hereditary nonpolyposis colorectal cancer. People with Lynch syndrome may have relatively few colon polyps, but those polyps can quickly become cancerous. Lynch syndrome is the most common inherited form of increased colon cancer risk and also is associated with cancers in other parts of the body, including the skin, stomach, uterus and bladder.

  If multiple members of a family have these cancers, especially if any one of them had them at an age younger than 50 years, it could be a sign that the family has a Lynch syndrome gene. Cancer risks are substantially lessened in people with Lynch syndrome who follow up regularly with their healthcare professionals for screening tests.

• Familial adenomatous polyposis (FAP), a rare condition that results in hundreds or even thousands of polyps in the lining of the colon in teenagers or young adults. If the polyps aren't treated, the risk of developing colon cancer is nearly 100%, usually before age 40. The risks are lessened through regular colon cancer screening tests as well as surgery to remove the affected colon, called colectomy. Genetic testing can help determine the risk of FAP.
• MUTYH-associated polyposis (MAP), a condition similar to FAP that is caused by changes in the MUTYH gene. People with MAP often develop multiple adenomatous polyps and colon cancer at a young age. Genetic testing can help determine the risk of MAP.
• Peutz-Jeghers syndrome, a condition that usually begins with freckles developing all over the body, including the lips, gums and feet. Then noncancerous polyps develop throughout the intestines. These polyps may become cancerous, so people with this condition have a higher risk of colon cancer.
• Juvenile polyposis syndrome (JPS), an inherited condition that is most common in children ages 1 to 7, though it sometimes happens in adults. Juvenile polyps are often single, but if there are multiple polyps, the risk of cancer is higher.
• Serrated polyposis syndrome is most often a condition that is not inherited but defined based on polyp history. People with multiple serrated lesions may have this syndrome. Because these polyps may become cancerous, they need to be taken out. People with this syndrome have colonoscopies more often.

Some colon polyps may become cancerous. The earlier polyps are taken out, the less likely it is that they will become cancerous.

The risk of colon polyps and colorectal cancer may be greatly reduced by having regular screenings. Certain lifestyle changes also can help:

• Adopt healthy habits. Include plenty of fruits, vegetables and whole grains in your diet and reduce your fat intake. Limit alcohol and quit all tobacco use. Stay physically active and keep a healthy body weight.
• Consider your options if you're at high risk. If you have a family history of colon polyps, talk with a healthcare professional. If you have a personal history of 10 or more neoplastic polyps, consider having genetic counseling. Referral to a genetic counselor also may be considered depending on your family history. If you've been diagnosed with a hereditary disorder that causes colon polyps, you'll usually need regular colonoscopies starting in young adulthood.

Screening tests are important for finding polyps before they become cancerous. These tests also can help find colorectal cancer in its early stages, when you have a good chance of recovery.

Screening methods include:

• Colonoscopy. In this test, a small tube with a light and camera is inserted through the rectum to examine the entire colon. The tube is guided through the colon using air to distend the colon and to get a clear view. Images of the lining of the colon are shown in real time on a video screen. Polyps usually appear as bumps or slightly raised spots or patches on an otherwise smooth lining. If polyps are found, the healthcare professional may take them out right away or take tissue samples to send to a lab for analysis. There also is the possibility of finding other areas of concern in the colon that can be sampled at the time of the exam.
• Virtual colonoscopy. This test uses a CT scan to view the colon. Virtual colonoscopy calls for the same bowel preparation as a colonoscopy. If a polyp is found during the scan, you'll need a colonoscopy to have the polyp examined and removed.
• Flexible sigmoidoscopy. Like a colonoscopy, this test uses a small tube with a light and camera but examines just the last third of the colon. Most of the colon is not seen with this screening test, so some polyps and cancers may not be found. When this test is used, it is repeated more often than colonoscopy or is used along with a yearly stool-based test.
• Stool-based tests. There are a few of these tests available. One of these checks for blood in the stool and needs to be repeated every year. Another test checks for blood and tumor markers in the stool to look for colon polyps or colorectal cancer and is repeated every three years. If the results of a stool-based tests are positive, a colonoscopy is recommended soon afterward.
• Blood-based testing. There is an FDA-approved blood screen for colon cancer. It needs to be repeated every three years. If positive, a colonoscopy is recommended to check for colon cancer.

A healthcare professional is likely to take out all polyps found during a bowel exam. Options for removal include:

• Polypectomy. During a colonoscopy, polyps can be taken out using a few techniques, a process called polypectomy. Very small polyps may be taken out with forceps. Small to medium polyps are usually taken out with a wire loop called a snare. Sometimes an electric current is applied to cut the polyp and prevent bleeding. Removing polyps prevents them from having the chance to grow into colorectal cancer.
• Minimally invasive surgery. Polyps that are too large or that can't be removed safely during colonoscopy are usually removed surgically. This is often done by placing an instrument called a laparoscope into the abdomen to remove the part of the bowel with the polyp or cancer.
• Total proctocolectomy. If you have a rare inherited syndrome, such as FAP, you may need surgery to remove your colon and rectum. This surgery can protect you from getting colorectal cancer.

Some colon polyps have the potential to become cancerous and others don't. A medical professional who studies tissue samples, called a pathologist, looks at the polyp tissue under a microscope to find out what type of polyp you have.

Follow-up care

If you have had an adenomatous polyp or a serrated lesion, you are at increased risk of colorectal cancer. The level of risk depends on the size, number and characteristics of the polyps that were taken out.

A healthcare professional is likely to recommend repeating a colonoscopy:

• In 7 to 10 years if you had only one or two small adenomas.
• In 3 to 5 years if you had three or four adenomas.
• In three years if you had 5 to 10 adenomas, adenomas larger than 10 millimeters in diameter or certain types of adenomas.
• In 6 months to one year if you had more than 10 adenomas, a very large adenoma or an adenoma that had to be taken out in pieces.

The follow-up colonoscopy schedule for serrated lesions is like that for adenomas.

Preparing for your colonoscopy

It's very important to fully clean out your colon before a colonoscopy. If stool remains in the colon and blocks the view of the colon wall, you will likely need another colonoscopy sooner than usual to make sure all polyps are found.

After good colon preparation, stool should appear as clear liquid. It may be slightly yellow or green depending on any liquids used while preparing. If you have trouble with your colon preparation or think that you have not fully cleaned out your colon, tell the health professional before beginning your colonoscopy. Some people need to take more steps to prepare for a colonoscopy.

If you take medicines that affect bleeding, such as aspirin or other medicines used for heart disease or blood clots, tell your healthcare team. Do not stop taking any medicines on your own. Your care team lets you know whether to keep taking them or pause them before your colonoscopy. The team also tells you how and when to start taking them again if needed.

You may be referred to a healthcare professional who specializes in digestive diseases, called a gastroenterologist.

What you can do

• Be aware of anything you need to do ahead of time, such as not eating solid food on the day before your appointment.
• Write down your symptoms, including any that may not seem related to the reason why you scheduled the appointment.
• Make a list of all your medicines, vitamins and supplements.
• Write down your key medical information, including other conditions.
• Write down key personal information, including any recent changes or stressors in your life.
• Ask a relative or friend to go with you to help you remember what the health professional says.
• Write down questions to ask during the appointment.

Questions to ask your doctor

• What's the most likely cause of my symptoms?
• What kinds of tests do I need? Do these tests require any special preparation?
• What treatments are available?
• What are the chances these polyps are cancerous?
• Is it possible that I have a genetic condition leading to colon polyps?
• What kind of follow-up testing do I need?
• Should I remove or add any foods to my diet?
• I have other health conditions. How can I best manage these conditions together?

In addition to the questions that you've prepared, don't hesitate to ask other questions during your appointment.

What to expect from your doctor

You'll likely be asked a few questions. Being ready to answer them may leave time to go over points you want to spend more time on. You may be asked:

• When did you first begin having symptoms, and how bad are they?
• Do your symptoms happen all the time or do they come and go?
• Have you or has anyone in your family had colorectal cancer or colon polyps?
• Has anyone in your family had other cancers of the digestive tract, the uterus, the ovaries or the bladder?
• Do you smoke or drink? If so, how much?