Types of bowel cancer
Bowel cancer isn't one disease – it can take different forms depending on where it starts and what's driving it. Understanding the type helps guide treatment.
At a glance
Click any row to jump to the full description below.
| Type | Where it starts | Share / context | Key signal |
|---|---|---|---|
| Colon cancer | Colon (large bowel) | ~2/3 of cases | Changes in bowel habits, blood, anaemia |
| Rectal cancer | Rectum (last 15 cm) | ~1/3 of cases | Rectal bleeding, incomplete emptying, narrow stool |
| Anal cancer | Anal canal | Rare (~1%) | Bleeding, anal pain, lump |
| Polyps (adenomas) | Bowel lining | Pre-cancer | Usually none — found on screening |
| Inflammatory bowel disease | Colon + small bowel | Risk factor | Diarrhoea, cramping, blood (chronic) |
| Lynch & hereditary | Genetic predisposition | 5–10% of cases | Strong family history, often early onset |
Colon cancer
- Where
- Colon (large bowel)
- Share
- ~2/3 of cases
- Signal
- Changes in bowel habits, blood, anaemia
Rectal cancer
- Where
- Rectum (last 15 cm)
- Share
- ~1/3 of cases
- Signal
- Rectal bleeding, incomplete emptying, narrow stool
Anal cancer
- Where
- Anal canal
- Share
- Rare (~1%)
- Signal
- Bleeding, anal pain, lump
Polyps (adenomas)
- Where
- Bowel lining
- Share
- Pre-cancer
- Signal
- Usually none — found on screening
Inflammatory bowel disease
- Where
- Colon + small bowel
- Share
- Risk factor
- Signal
- Diarrhoea, cramping, blood (chronic)
Lynch & hereditary
- Where
- Genetic predisposition
- Share
- 5–10% of cases
- Signal
- Strong family history, often early onset
Most common · ~2/3 of cases
Colon cancer
Colon cancer is the most common type of bowel cancer. It starts in the colon (the longest part of the large bowel) and accounts for roughly two-thirds of all bowel cancer cases.
The colon is divided into sections: the ascending colon (right side), transverse colon (across the top), descending colon (left side), and sigmoid colon (leading to the rectum). Cancer can develop in any of these sections, though left-sided cancers are more common.
Right-sided colon cancers may cause different symptoms than left-sided ones. Right-sided cancers are more likely to cause anaemia and fatigue, while left-sided cancers more often cause changes in bowel habits and visible blood in the stool.
~1/3 of cases · pelvic surgery often needed
Rectal cancer
Rectal cancer starts in the rectum, the last 15 centimetres of the large bowel. It makes up about one-third of bowel cancer cases.
Because of the rectum's location deep in the pelvis, treatment for rectal cancer can differ from colon cancer. Surgery may be more complex, and radiation therapy is more commonly used. Some people with rectal cancer may need a temporary or permanent stoma (an opening in the abdomen for waste to leave the body).
Common symptoms include rectal bleeding, a feeling of incomplete emptying, and changes in stool shape or consistency.
Rare · distinct from bowel cancer
Anal cancer
Anal cancer is less common and is different from colon or rectal cancer. It develops in the anal canal – the short passage at the very end of the digestive tract.
While it is sometimes grouped under "bowel cancer," anal cancer has different causes and treatments. It is often linked to the human papillomavirus (HPV) and is usually treated with a combination of chemotherapy and radiation rather than surgery.
Symptoms may include bleeding, pain or pressure in the anal area, and changes in bowel habits. Because these symptoms are often attributed to haemorrhoids, anal cancer can be missed – so it's important to see your GP if symptoms persist.
Pre-cancer · usually no symptoms
Polyps (adenomas)
Polyps are small growths on the inner lining of the bowel. They are very common, especially in people over 50. Most polyps are harmless and will never become cancer.
However, a type called adenomatous polyps (adenomas) can slowly change over time and eventually develop into cancer. This process usually takes 5 to 10 years, which is why regular screening is so effective – polyps can be found and removed during a colonoscopy before they become dangerous.
There are different types of polyps:
- •Adenomatous polyps – the most common pre-cancerous type
- •Sessile serrated polyps – flat polyps that can be harder to detect and may carry a higher risk
- •Hyperplastic polyps – generally considered low-risk
If polyps are found during a colonoscopy, they are usually removed at the same time. Your specialist will recommend a follow-up schedule based on the number, size, and type of polyps found.
Risk factor · ongoing inflammation
Inflammatory bowel disease (IBD)
Inflammatory bowel disease is not cancer, but long-standing IBD can increase your risk of developing bowel cancer. The two main forms of IBD are:
- •Ulcerative colitis (UC) – causes inflammation and ulcers in the colon and rectum
- •Crohn's disease – can affect any part of the digestive tract, but most commonly the end of the small bowel and the colon
The risk of bowel cancer increases the longer you have had IBD and the more of the bowel that is affected. If you have IBD, your specialist will usually recommend regular colonoscopy surveillance to check for early changes.
IBD is different from irritable bowel syndrome (IBS). IBS does not increase bowel cancer risk.
5–10% of cases · runs in families
Lynch syndrome & hereditary bowel cancer
Around 5–10% of bowel cancers are caused by inherited gene changes. The most common hereditary condition is Lynch syndrome (also called hereditary non-polyposis colorectal cancer, or HNPCC).
People with Lynch syndrome have a much higher lifetime risk of bowel cancer (up to 80%) and often develop it at a younger age. Lynch syndrome also increases the risk of other cancers, including uterine, ovarian, and stomach cancer.
Other hereditary conditions include:
- •Familial adenomatous polyposis (FAP) – causes hundreds or thousands of polyps in the bowel, usually diagnosed in the teens or twenties
- •MUTYH-associated polyposis (MAP) – a rarer condition causing multiple polyps
If you have a strong family history of bowel cancer – especially if relatives were diagnosed before age 50 – talk to your GP about genetic counselling and earlier screening.
Concerned about hereditary risk?
If bowel cancer runs in your family, you may benefit from earlier screening or genetic counselling. Talk to your GP or contact us.