The small bowel makes up most of the digestive system and helps your body to digest food and take in vitamins. Cancer that starts here is called small bowel cancer.
The small bowel is between 4 and 6 metres long and is made up of 3 parts. The:
- duodenum (dew-oh-dean-um) – the top part of the small bowel, which connects to the stomach
- jejunum (jej-you-num) – the middle part
- ileum (ill-ee-um) – the lower part, which connects to the large bowel (colon)
Most cases of small bowel cancer are found in the duodenum.
How common are small bowel cancers?
Cancers of the small bowel are rare. Around 1,800 people are diagnosed in the UK each year.
Whereas, around 42,900 cases of cancer of the large bowel (colon) are diagnosed each year.
Risks and causes
We don’t know what causes most small bowel cancers. But there are some factors that may increase your risk.
- age - small bowel cancer is more common in older people.
- familial adenomatous polyposis – a rare condition where an inherited faulty gene makes many polyps develop on the bowel lining
- Lynch syndrome (Hereditary non polyposis colorectal cancer or HNPCC) - a gene fault that increases the risk of several different types of cancer at a younger age
- Peutz Jeghers syndrome – an inherited condition where benign (non cancerous) polyps form in the bowel.
- Crohn’s disease – cancers related to Crohn’s disease are usually adenocarcinomas of the ileum. Only 2 out of 100 people with Crohn's disease (2%) will develop cancer in the small bowel
- Coeliac disease – may slightly increase your risk of developing lymphoma or adenocarcinoma of the small bowel. Sticking to a gluten free diet reduces the risk
- a diet rich in red meat or smoked foods, or a high fat diet
Smoking and drinking alcohol has also been linked to the risk of small bowel cancer, but we need further research to confirm this.
Types of small bowel cancer
Tumours of the small bowel may be either non cancerous (benign) or cancerous (malignant). Benign tumours include polyps and lipomas
There are different types of malignant small bowel tumour.
Around 40 out of 100 small bowel cancers (around 40%) are adenocarcinomas, making it the most common type. It starts in cells that line the bowel (epithelial cells) and develops most often in the duodenum.
Around 40 out of 100 small bowel tumours (around 40%) are neuroendocrine which includes carcinoid tumours. These develop from cells that produce hormones, most commonly in the appendix or the ileum.
Around 15 out of 100 small bowel cancers (around 15%) are lymphomas, usually found in the jejunum.
Sarcomas can develop in the soft tissues anywhere in the small bowel, but most often grow in the ileum. There are different types and the most common is a cancer of smooth muscle (leiomyosarcoma).
Gastrointestinal stromal tumours are a rare type of sarcoma that start in the connective tissue in the small bowel.
These are tumours that have started somewhere else in the body and have spread to the small bowel. These cancer cells have to be treated in the same way as your primary cancer type. The most common cancers to spread to the small bowel include, ovarian and pancreatic cancers.
It's important to read about your type of primary cancer to get the right information and support for you.
You usually start by seeing your GP. They will ask you about your general health and symptoms and will also examine you.