Pseudomyxoma peritonei (PMP) is a rare, usually slow-growing, cancer of the appendix.
Pseudomyxoma peritonei (PMP) usually begins as a slow-growing tumor in the appendix, called a Low-Grade Mucinous Appendiceal Neoplasm (LAMN). Rarely, PMP starts in other parts of the bowel, ovary or bladder.
Over time, the tumor produces a jelly-like substance called mucin. This can cause the appendix to swell up like a balloon. The tumor can then break through the wall of the appendix and spread tumor cells into the lining of the tummy (the peritoneum).
The tumor cells and mucin build up in the lining of the tummy, putting pressure on the bowel and causing symptoms. It can be many years before symptoms become obvious. Unlike other cancers, PMP rarely spreads via the lymphatic system or the bloodstream. It usually remains inside the tummy, spreading along its internal surfaces.
Causes of pseudomyxoma peritonei
The cause of PMP is unknown.
Signs and symptoms of pseudomyxoma peritonei
Most people don't have any symptoms for a long time. When symptoms occur they may include any of the following:
- slow increase in waist size
- hernia (a swelling on the abdomen)
- loss of appetite
- unexplained weight gain
- abdominal or pelvic pain
- changes in bowel habits
Most people with these symptoms won't have PMP, but it's important to have any symptoms checked by your doctor.
How pseudomyxoma peritonei is diagnosed
PMP can be difficult to diagnose. It may be found during investigations into abdominal symptoms, or it may be discovered during an operation for another problem.
CT (computerized tomography) scan
A CT scan takes a series of x-rays that build up a three-dimensional picture of the inside of the body. The scan is painless. It can help to find where the tumor started and check whether it has spread within the abdomen. It usually takes 10-30 minutes. CT scans use a small amount of radiation, which is very unlikely to harm you and won't harm anyone you come into contact with. You will be asked not to eat or drink for at least four hours before the scan.
You may be given a drink or injection of a dye, which allows particular areas to be seen more clearly. For a few minutes, this may make you feel hot all over. If you are allergic to iodine or have asthma you could have a more serious reaction to the injection, so it's important to let your doctor know beforehand.
Sometimes the pictures from the CT scan are enough to make the diagnosis, but sometimes biopsies or an operation are needed to be sure of the diagnosis of PMP.
The treatment of PMP depends on a number of factors. These include how far the tumor has spread and your general health. Some of the standard cancer treatments, such as radiotherapy, aren't suitable for treating PMP. This is because PMP cells aren't sensitive to radiotherapy and they are often spread over too large an area for this treatment.
You may be offered surgery to treat this kind of cancer. There are two types of surgery:
- Cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (HIPEC).
- Debulking surgery.
Cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (HIPEC)
This may be an option for some people. It‘s an intensive treatment that aims to remove the tumor to try to cure PMP. It is also known as the Sugarbaker technique (named after the surgeon who first developed it). It involves removing the lining of the abdomen or organs such as the bowel, omentum (fatty tissue in the tummy) and gallbladder. In women, the womb (uterus) and ovaries may also be removed. About half (50%) of people who have a Sugarbaker operation will need a stoma (colostomy). Most of the stomas are temporary and will be reversed after about six months.
Once the surgeon has removed all or most of the tumor, a heated chemotherapy drug is put in the tummy (hyperthermic intraperitoneal chemotherapy) for 90 minutes during the operation. The combination of the chemotherapy drug and heat aims to kill any tumor cells that are left behind.
This is a major operation and may take up to 10 hours. Afterwards, you’ll be nursed in a critical care unit for several days and will stay in hospital for about 2 weeks. This operation has potentially serious complications and the surgeon will discuss these with you.
It's very important to discuss this operation with specialist doctors, as the Sugarbaker technique is a very complicated procedure and isn't suitable for everyone. It should only be carried out at a specialist center.
This is done when it’s not possible to have cytoreductive surgery. It aims to remove as much of the tumor as possible to reduce the symptoms of the cancer. This may involve removing the omentum (fatty tissue in the tummy) and part of the bowel. In women, the womb (uterus) and ovaries may also be removed.
Unfortunately, this surgery will not take away all the tumor cells and the PMP is likely to grow back. Further debulking operations may be needed. However, each operation becomes more difficult to do, with less benefit and more risks of complications each time.
Sometimes, a permanent stoma is needed after debulking surgery. It can help to prevent the bowel from becoming blocked (obstructed). Your specialist nurse can give you more information about looking after a stoma.