About pseudomyxoma peritonei

Pseudomyxoma peritonei (PMP) is a very rare type of cancer. It usually begins in your appendix as a small growth, called a polyp. This is different to polyps that cause bowel cancer and is called a Low Grade Appendiceal Mucinous Neoplasm (LAMN).

Pseduomyxoma peritonei is pronounced SOO-doh-mix-OH-muh  PAYR-ih-TOH-nee-EYE. 

More rarely, it can start in:

  • other parts of the bowel
  • the ovaries
  • the bladder

This polyp eventually spreads through the wall of your appendix or wherever else it starts. It then spreads cancerous cells to the abdominal cavity lining (the peritoneum). These cancerous cells produce mucus. The mucus collects in the abdomen as a jelly like fluid called mucin. PMP is sometimes called ‘Jelly Belly’.

Doctors often call PMP a borderline malignant condition. Malignant means cancerous. Cancers usually spread to other parts of the body through the lymphatic 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 tummy (abdomen).

The appendix and peritoneum

Your appendix is part of the digestive system. It’s on the right hand side of your abdomen and is attached to your colon (large bowel). The role of the appendix is unclear.

Diagram showing the position of the appendix

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
Diagram showing the peritoneum and peritoneal fluid in the abdomen

The space between these layers is called the peritoneal space. The peritoneum also makes a lubricating fluid (peritoneal fluid). It helps the organs inside move smoothly against each other as you move around.

How does pseudomyxoma peritonei spread?

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.

What causes pseudomyxoma peritonei?

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.  

What are the symptoms of pseudomyxoma peritonei?

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. Ovarian cancer may also cause a swollen abdomen. Some types of ovarian cancer cells also produce mucin. 

Symptoms can include:

  • abdominal or pelvic pain
  • not being able to become pregnant
  • abdominal swelling and bloating
  • changes in bowel habits
  • hernia (a bulge in the tummy wall or groin)
  • loss of appetite
  • feeling of fullness

Often, pseudomyxoma peritonei is only properly diagnosed after an operation to look into the tummy (abdomen). This is also 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:

  • ultrasound scan
  • CT scan
  • MRI scan

What is the treatment for pseudomyxoma peritonei?

The main treatments for pseudomyxoma peritonei (PMP) are surgery and chemotherapy. 

  • Epithelial tumors of the appendix

    N Melnitchouk and others

    UpToDate website

    Accessed 27 January 2022

  • Cancer: Principles and Practice of Oncology (11th edition)

    VT De Vita, TS Lawrence and SA Rosenberg

    Lippincott, Williams and Wilkins, 2019

  • Pseudomyxoma Peritonei

    B Yu and M Raj

    In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 January

  • Ross and Wilson​ Anatomy and Physiology in Health and Illness (13th edition)
    A Waugh and A Grant
    Elsevier, 2018

Last reviewed: 
31 Jan 2022
Next review due: 
31 Jan 2025

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