Pseudomyxoma peritonei
Pseudomyxoma peritonei (PMP) usually begins in your as a small growth, called a . This is different to polyps that cause . It is called a Low Grade Appendiceal Mucinous Neoplasm (LAMN).
It can start in other places such as the bowel or ovary. But this is even rarer.
It usually grows slowly. But it can eventually spread into other parts of the tummy area (abdomen). It spreads to the which lines the abdomen. The cancer cells make . The mucus collects in the abdomen as a jelly like fluid called mucin. Doctors sometimes call PMP ‘Jelly Belly’.
They also call PMP a borderline condition. Cancers usually spread to other parts of the body through the and blood system. PMP doesn’t behave like this and it doesn’t spread to other parts of the body. But it does grow and spread inside the abdomen.
Your appendix is part of the . It’s on the right hand side of your abdomen and is attached to your (large bowel). The role of the appendix is unclear.
The sheet of tissue covering the organs of your abdomen is called the peritoneum. The peritoneum has 2 layers:
the parietal layer lines the abdominal wall
the visceral layer covers the organs
The space between these layers is called the peritoneal space. The peritoneum also makes a lubricating fluid (peritoneal fluid). It helps the inside move smoothly against each other as you move around.
Pseudomyxoma peritonei doesn't act like most cancers. It rarely spreads through the bloodstream or the lymphatic system to any other part of the body.
Instead, it spreads inside the abdomen. The cancer cells generally spread by following the peritoneal fluid flow. They attach to the peritoneum at particular sites. Here they produce mucus which collects inside the abdomen and eventually causes symptoms. Without treatment, it will take over the peritoneal cavity. It can press on the bowel and other organs.
This condition develops very slowly. It might be years before you have any symptoms of this type of cancer. Because of this, it has usually spread beyond the appendix before diagnosis.
We don't know what causes this type of cancer. Most cancers are caused by a number of different factors working together.
Pseudomyxoma peritonei is more common in women than men.
Some people won't have any symptoms of pseudomyxoma peritonei. So it can be difficult to diagnose.
In women, this type of cancer can sometimes be confused with . Ovarian cancer may also cause a swollen abdomen. Some types of ovarian cancer cells also produce mucin.
Symptoms can include:
pain in your abdomen or
not being able to become pregnant
swelling and bloating in your abdomen
changes in bowel habits
hernia - this is a bulge in the tummy wall or groin
loss of appetite
feeling of fullness
Often, doctors can only diagnose pseudomyxoma peritonei properly after an operation to look into the abdomen. This operation is called a laparotomy.
It can be difficult to diagnose PMP. Doctors sometimes find it by accident during treatment for other conditions.
Before you have treatment, your doctors will arrange for you to have tests. The tests include:
The main treatments for pseudomyxoma peritonei (PMP) are and .
Last reviewed: 16 Apr 2025
Next review due: 16 Apr 2028
Treatment for pseudomyxoma peritonei (PMP) depends on the size of the tumour and your general health. Find out more about treatment options.
Rare cancers affect a small number of people. In the UK and Europe experts say it is rare if fewer than 6 in 100,000 people are diagnosed each year. Find out more about rare cancer.
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