Large bowel and rectal neuroendocrine cancers
Large bowel and rectal neuroendocrine cancers are rare cancers.
Read more about the difference between NETs and NECs
The colon is about 5 feet long and has 4 sections. The parts of the colon are:
ascending colon – runs up the right side of the tummy (abdomen) and is connected to the small bowel by the caecum
transverse colon – runs across the body, under the stomach
descending colon – runs down the left side of the abdomen
sigmoid colon – an ‘S’ shaped bend that joins the descending colon to the rectum
Neuroendocrine cancers can start in any of these sections.
Large bowel neuroendocrine cancers can be neuroendocrine tumours (NETs) or neuroendocrine carcinomas (NECs). You can also get neuroendocrine cancer cells mixed in a tumour with a more common type of bowel cancer cell. Doctors call this MiNEN or mixed Neuroendocrine nonNeuroendocrine Neoplasm.
Large bowel neuroendocrine cancers can spread to other parts of the body. The most common places where they can spread to are the:
liver
The back passage (rectum) starts in the last part of the large bowel. This part of the bowel stores poo (stool) until you are ready to pass it out of the body.
Most rectal neuroendocrine cancers are neuroendocrine tumours (NETs). Rectal neuroendocrine carcinomas (NECs) are less common. You can also get neuroendocrine cancer cells mixed in a tumour with a more common type of rectal cancer cell. Doctors call this MiNEN or mixed Neuroendocrine nonNeuroendocrine Neoplasm.
Rectal NETs are often slow growing and small tumours. But it is possible for them to spread. Around 10 to 20 out of every 100 rectal NETs (around 10 to 20%) may spread to nearby lymph nodes or beyond.
Around 370 people are diagnosed with a large bowel or rectal neuroendocrine cancer in England every year.
Rectal neuroendocrine cancers are more common than large bowel neuroendocrine cancers. Doctors often find rectal NETs when people are having tests for something else.
Some things increase the risk of developing neuroendocrine cancers. But having one of these risk factors doesn’t mean that you will definitely develop a cancer. A risk factor is anything that increases your risk of getting a disease. Different diseases have different risk factors.
Read more about the risks and causes of neuroendocrine cancer
Many people with large bowel or rectal neuroendocrine cancers don’t have symptoms. Doctors often diagnose it when doing tests for something else.
When you do have symptoms, they are usually caused by:
the growth of the cancer in your large bowel or rectum
the neuroendocrine cancer spreading to other parts of the body
hormones made by the cancer, but this is rare for bowel and rectal neuroendocrine cancer
Symptoms might be very similar to bowel cancer symptoms. They might include:
a change in your normal bowel habits, including diarrhoea or constipation or a change in the consistency of your poo
pain or discomfort in your tummy, back passage or
bleeding from your bowel or rectum – you might see some blood in your poo, or your poo might look black
unexplained weight loss, weakness or fatigue
Diarrhoea means having 2 or more loose bowel movements than usual.
Sometimes cancer can block the bowel. This is called bowel obstruction and symptoms of this include:
griping pain in the tummy
feeling bloated
constipation and being unable to pass wind
feeling sick
A bowel obstruction is an emergency. You should see your doctor quickly or go to A&E if you think you have a bowel obstruction.
Large bowel and rectal neuroendocrine cancers often don’t cause symptoms. Most people are diagnosed with when they are having tests for something else.
If you have symptoms, you usually see your GP first. They might organise some tests. This might include blood tests and a test to look inside your bowel (colonoscopy).
Your GP will decide if you need to see a specialist.
Find out more about seeing a specialist
If your doctor suspects cancer, you have tests to check the type of cancer you have. Tests also show the size of the cancer and whether it has spread. This helps your doctor plan your treatment.
Tests might include:
blood tests - these check your general health and check levels of substances raised by neuroendocrine cancer
or to look inside your bowel and take a cancer sample ()
of your chest and tummy
of your tummy and rectum
to show the size of the cancer and whether it has spread
radioactive scans – these are octreotide scans (or ) and MIBG scans
Read more about tests to diagnose neuroendocrine cancer
The tests and scans you have give information about:
your type of cancer
the grade of your cancer - this is how quickly or slowly the cancer cells are growing and dividing
the stage of your cancer - this is how big the cancer is, and whether it has spread
This information helps your doctor decide which treatment you need.
Read more about grades, types and stages of large bowel and rectal neuroendocrine cancer
The best person to talk to you about your outlook () is your doctor. Not everyone wants to know. People cope differently with cancer and want different information.
Survival depends on many factors. So no one can tell you exactly how long you will live. Your doctor might be able to give you some guide, based on their knowledge and experience.
Your prognosis will depend on whether you have a neuroendocrine carcinoma (NEC) or a neuroendocrine tumour (NET). And it will depend on where it is, and how far it has spread (stage).
Last reviewed: 20 Mar 2025
Next review due: 20 Mar 2028
The grade shows how quickly or slowly your cancer cells are dividing and growing. The stage refers to the size of the cancer, and whether it has spread.
Treatment depends on where the cancer started, its size and whether it has spread. Surgery is the main treatment for large bowel and rectal neuroendocrine cancer.
Treatment depends on the type of neuroendocrine cancer you have, where it is, its size and whether it has spread (the stage).
Survival (prognosis) depends on several factors. This includes your type of neuroendocrine cancer, where it is in your body, and whether it has spread.
Practical and emotional support is available to help you cope with neuroendocrine cancer.
Neuroendocrine cancers develop in cells of the neuroendocrine system. They can develop in different parts of the body including the lungs, stomach, pancreas and bowel.
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