What is small bowel cancer?

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.

Diagram showing the position of the small bowel

Diagram showing the parts of the small bowel

How common are small bowel cancers?

Cancers of the small bowel are rare. Around 1,900 people are diagnosed in the UK each year.

Whereas, around 44,100 cases of cancer of the large bowel (colon) and rectum 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 (FAP) – 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 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
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, smoking and obesity have all been linked to an increased risk of small bowel cancer.

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.

Adenocarcinoma

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.

Neuroendocrine cancers

Around 40 out of 100 (around 40%) of small bowel cancers are neuroendocrine cancers. These develop from cells that produce hormones, most commonly in the ileum.

Lymphoma

More than 15 out of 100 small bowel cancers (more than15%) are lymphomas, usually found in the jejunum

Sarcoma

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 (GIST) are a rare type of sarcoma that can start in the connective tissue in the small bowel.

Secondary cancers

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.

Getting diagnosed

You usually start by seeing your GP. They will ask you about your general health and symptoms and will also examine you.