Pseudomyxoma Peritonei (PMP): Overview and More

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Pseudomyxoma peritonei (PMP) is a very rare type of cancer that often grows slowly. It usually starts in your appendix as a small growth called a polyp. Sometimes it starts in another part of the bowel, the bladder, or the ovaries, but this is rare. Due to its slow-growing nature, it is usually discovered at an advanced stage, when it severely impacts quality of life.

While the most common cause of PMP is appendix cancer, other types of tumors can cause PMP. Read on to learn more about PMP, including symptoms to look for, how the cancer is diagnosed, and the treatments available.

The incidence of PMP is believed to be approximately one to three cases per million people per year.

Man with bloating and abdominal pain, overweight male body on gray background, studio shot

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Pseudomyxoma Peritonei Symptoms

PMP may not cause any problems until the tumor grows and spreads away from the area where it started (metastasized). When it enters your abdomen, more tumors form and make mucinous fluid, a jelly-like material. This eventually fills up your abdomen, which is sometimes referred to as "jelly belly."

Some of the symptoms of PMP include:

  • Gradual increase in waist size
  • A hernia (a bulge on the abdominal wall, or in the groin)
  • Loss of appetite
  • Unexplained weight gain
  • Abdominal or pelvic pain
  • Change in bowel habits
  • Appendicitis (inflammation of the appendix)

When mucinous fluid builds up in your abdomen, it can push on other body parts. This causes swelling and digestion issues. It can even block your intestines, which can be very serious and even life-threatening. Seek urgent medical attention if you have severe or persistent abdominal pain, distention, or vomiting.

Causes

The exact cause of pseudomyxoma peritonei is not known. There are no genetic, familial, or environmental factors known to cause this disorder.

PMP develops from a perforation (hole) in the appendix that is caused by the penetration of a small polyp located within the appendix. The tumor cells from the appendix spread within the abdominal and pelvic cavity.

Various types of tumors can lead to PMP, and it is not known why some cause PMP and others do not. Appendix tumors are the most common tumors associated with PMP, but tumors of the ovary, colon, stomach, and pancreas have also been reported in people with PMP.

Diagnosis

PMP is typically diagnosed between the ages of 40 and 55 and is often found incidentally in patients undergoing laparotomy (a surgery where the abdomen is opened via a large incision), laparoscopy (a procedure where a surgical tool with a camera on the end is inserted in the abdomen via a small incision), or imaging for other medical conditions.

To find out if you have PMP, your doctor will examine you and ask questions about your symptoms. Then they'll want to get pictures of inside your belly and other areas of your body.

The following tests may be used to diagnose PMP:

  • CT scan: A CT (computed tomography) scan takes pictures of the inside of the body using X-rays taken from different angles. A computer combines these pictures into a detailed, 3D image that shows any abnormalities or tumors.
  • MRI scan: An MRI (magnetic resonance imaging) scan uses magnetic fields, not X-rays, to produce detailed images of the body. MRI can be used to measure the tumor’s size.
  • Biopsy: A biopsy is the removal of a small amount of tissue for examination by a specialist called a pathologist. It is this examination that will ultimately lead to a diagnosis of PMP. Because of the nature of PMP, this biopsy will likely take place during surgery, for example, to remove the appendix.
  • Blood tests: Some tumor markers (compounds released by cancer cells, or by the immune system in response to cancer cells) in the blood have been shown to indicate appendix cancer and/or PMP activity, particularly CEA, CA-125, and CA 19-9. Unfortunately, tumor markers are not accurate indicators for everyone. 

Treatment

The main treatments for PMP are surgery and chemotherapy. Your treatment may depend on how far the PMP has spread and your general health. It is important that you discuss the pros and cons of your treatment options with your specialist.

Surgery Combined with Chemotherapy

When possible, you’ll have surgery combined with chemotherapy directly into your abdomen. It's called cytoreductive surgery (CRS) with hyperthermic intraperitoneal chemotherapy (HIPEC). The aim is to remove all of the visible PMP cells in your abdomen so there are no cancer cells left that could start to grow again.

You have to be well enough to have this intensive surgery. And the surgeon needs to be able to remove the disease without affecting your vital organs.

The procedure involves:

  • The surgeon removing any tissue affected by PMP
  • Sending heated chemotherapy drugs directly into your abdomen during the surgery (HIPEC)

Chemotherapy uses anticancer (cytotoxic) drugs to destroy cancer cells. The aim is to kill any cancer cells that are left behind. After 60–90 minutes, the chemotherapy liquid is drained from the abdomen and the surgeon finishes the operation.

This is a major surgery. The operation can take around 10 hours and your recovery can be slow. Sometimes people need more than one operation, several months apart.

Debulking surgery

If it is not possible to remove all the PMP with cytoreductive surgery, you may have a type of surgery called debulking surgery. This is when the surgeon removes as much of the PMP as possible. The doctor may also remove the omentum (a large fatty structure that hangs over the intestines) and part of the bowel.

The aim of this surgery is to reduce the symptoms. This treatment will not remove all of the PMP. You may need to have more debulking surgery later.

Chemotherapy

You might have chemotherapy if you can’t have surgery. You are more likely to need chemotherapy if:

  • Your cancer is causing symptoms and affecting your quality of life.
  • CT scans show your cancer is growing quickly.

Active Surveillance

Your doctor might decide to closely monitor your cancer if it’s small and growing slowly and you don’t currently need treatment. Your doctor will check up on you regularly. Active surveillance can also sometimes be called a watch-and-wait approach.

Prognosis

Outcomes in patients with PMP are strongly associated with tumor biology. In tumors that are slow-growing and able to be treated with surgery, the prognosis is good. Analysis of data from the Memorial Sloan-Kettering Cancer Center found the median survival of the patient population was 9.8 years from the date of the operation.

However, recurrence of PMP is common. Treatment may be beneficial, particularly in controlling symptoms, but an absolute cure is uncommon.

Summary

Pseudomyxoma peritonei (PMP) is a very rare form of cancer that often grows slowly. You may not notice any symptoms until the tumor has spread from where it started. With surgery and chemotherapy, the prognosis for this cancer is good.

A Word From Verywell

If you are worried about unexplained weight gain, a change in bowel habits, and swelling in your abdomen, speak to your healthcare provider. While this could be the sign of a noncancerous condition, it's best to rule out dire reasons for these symptoms. If you are diagnosed with PMP, take heart: While it isn't entirely curable, it is treatable.

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