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About pseudomyxoma peritonei

Pseudomyxoma peritonei is a very rare type of cancer. It usually begins in your appendix as a small growth, called a polyp.

Or, more rarely, it can start in other parts of the:

  • bowel
  • ovary
  • bladder

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

Doctors often call PMP a borderline malignant condition. Malignant means cancerous. Cancers 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 abdomen.

Pseduomyxoma peritonei is pronounced sue-doh-mix-oh-ma pery-ton-i.

The appendix and peritoneum

Your appendix is part of the digestive system. It’s on the right hand side of your abdomen and it’s 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 fluid in the abdomen

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

How pseudomyxoma peritonei spreads

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 spread and grow on to the peritoneum. They produce mucus which collects inside the abdomen and eventually causes symptoms. Without treatment it eventually takes over the peritoneal cavity and presses on the bowel and other organs

This condition develops very slowly and it might be years before you have any symptoms from 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.  

Symptoms of pseudomyxoma peritonei

Some people won't have any symptoms, so pseudomyxoma peritonei can be difficult to diagnose.

In women, this type of cancer can sometimes be confused with ovarian cancer because 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 abdomen (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


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

Last reviewed: 
10 Aug 2018
  • Cancer of the appendix and pseudomyxoma peritonei
    UpToDate, Accessed 2018

  • Treatment of peritoneal surface malignancies with hyperthermic intraperitoneal chemotherapy—current perspectives
    J Spiliotis and others
    Curr Oncol, 2016. Vol 23, Issue 3, Pages 266-275.