Colorectal cancer

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Precancerous conditions of the colon or rectum

Precancerous conditions of the colon or rectum are changes to cells that make them more likely to develop into cancer. These conditions are not yet cancer. But if they aren’t treated, there is a chance that these abnormal changes may become colorectal cancer.


Adenomas (adenomatous polyps) are abnormal growths attached to the lining of the colon or rectum.

Dysplasia describes changes to cells. Mild (low-grade) dysplasia means the cells are slightly abnormal. Severe (high-grade) dysplasia means the cells look very abnormal and more like cancer cells.

Types of adenomas

The types of adenomas are described based on the growth pattern of cells, which is how the cells look when viewed under a microscope. The 3 types of adenomas are:

  • Tubular adenomas are the most common type. The cells in these adenomas look like tubes.
  • Villous adenomas have cells with finger-like growths. They are often larger than tubular adenomas.
  • Tubulovillous adenomas have cells with both tubular and villous growth patterns.

Risk factors

Your risk of having adenomas is higher if you have a family history of polyps, a hereditary colorectal syndrome or colorectal cancer.


Most adenomas do not cause any symptoms. If symptoms develop, they can include:

  • diarrhea
  • mucus in the stool
  • bleeding from the rectum
  • cramps or abdominal pain
  • anemia


If you have symptoms or your doctor thinks you might have adenomas, you will be sent for tests. The diagnosis is usually made by a colonoscopy. Other tests that may be done are:

  • digital rectal exam (DRE)
  • barium enema
  • flexible sigmoidoscopy
  • biopsy

Find out more about these tests and procedures.

Treatments and follow-up

The most common treatment for an adenoma is to remove it during a colonoscopy or sigmoidoscopy. Depending on the number and type of adenomas and how severe the dysplasia is, a bowel resection may be done. Your doctor may suggest you have regular follow-up with a colonoscopy or sigmoidoscopy to check for more adenomas.

Hereditary colorectal syndromes

The following rare hereditary colorectal syndromes are precancerous conditions of the colon or rectum. These syndromes are caused by a changed (mutated) gene that can be passed from parents to children.

  • Lynch syndrome (hereditary non-polyposis colorectal cancer or HNPCC) is the most common type of hereditary colorectal syndrome. A single polyp or a few polyps develop in the colon or rectum.
  • Familial adenomatous polyposis (FAP) causes hundreds to thousands of polyps to develop on the lining of the colon and rectum.
  • Peutz-Jeghers syndrome causes many hamartomas to grow in the digestive tract, including the colon and rectum.
  • Juvenile polyposis syndrome causes hamartomas to grow in the digestive tract, including the colon and rectum. These hamartomas usually form before age 20. Some people develop only a few hamartomas while others have over 100 hamartomas.

Risk factors

Your risk of having a hereditary colorectal syndrome depends on if family members have one of the mutated genes linked to the syndrome.


The symptoms of a hereditary colorectal syndrome depend on the type of syndrome and the number of polyps in the colon and rectum. You may not have any symptoms. When there are many polyps, they can cause:

  • changes in bowel habits
  • bleeding from the rectum
  • pain or discomfort in the abdomen
  • anemia
  • a blockage in the intestine (called a bowel obstruction)


If you have symptoms or your doctor thinks you might have a hereditary colorectal syndrome, you will be sent for tests. Tests used to diagnose a hereditary colorectal syndrome may include:

  • colonoscopy
  • gastroscopy
  • biopsy
  • genetic testing

Find out more about these tests and procedures and genetic testing.

Treatment and follow-up

Treatments offered for hereditary colorectal syndromes depend on the number of polyps and if you have symptoms. Treatments may include:

  • removal of polyps (polypectomy)
  • bowel resection with removal of all of the colon (total colectomy)
  • bowel resection with removal of the rectum and part of the sigmoid colon (proctocolectomy)

You will have regular screening with colonoscopy or sigmoidoscopy, as well as other tests. These tests are done to check the polyps and find cancer if it develops.


A small growth on a mucous membrane, such as the lining of the colon, bladder, uterus (womb), vocal cords or nasal passage.

Most types of polyps are non-cancerous, but some have the potential to become cancer.


A non-cancerous (benign) tumour-like mass caused by an overgrowth of normal cells. 


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