How Pseudomyxoma Peritonei (PMP) Is Diagnosed

Pseudomyxoma peritonei (PMP) is a cancer that often grows slowly. It usually starts in the appendix and is difficult to diagnose.

To diagnose PMP, several tests are available, including a biopsy, imaging scans, and blood tests. Often, PMP can be found during treatment for another disease or an operation for other medical problems.

Doctors working on a CT scan

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Self-Checks/At-Home Testing

It's not possible to self-diagnose PMP but you can keep track of any symptoms you have to speak to your doctor about them.

PMP makes a jelly-like substance called mucin that can spread from the appendix (the narrow pouch projecting from the colon, or large intestine) into the abdomen. Eventually, the buildup of mucin puts pressure on the bowel and other organs and can cause symptoms.

You may not have any symptoms at first. But some of the following may appear over time:

Physical Examination

A physical examination can help a doctor diagnose PMP. But because PMP has similar symptoms as other noncancerous conditions, PMP may require more than a physical exam to be diagnosed.

Your doctor may palpate your belly to feel for any obvious masses that may be present in advanced disease. In women, ovaries may be enlarged and PMP may be mistaken for ovarian cancer.

Labs and Tests

PMP is often diagnosed incidentally in patients undergoing surgery such as laparotomy (surgery of the abdomen) or laparoscopy (minimally invasive surgery) for other medical conditions such as appendicitis.

When tumors and mucin are found during an operation, diagnosis is given after samples of tissue are sent to a lab for tests (biopsy). Because of the rarity of PMP, many pathologists (medical doctors who examine body tissues) may not recognize PMP cells at first and it may not be properly diagnosed.

Your doctor may also order blood tests to look for something called tumor markers, anything produced by cancer cells or in response to cancer. Some tumor markers in the blood that have been shown to indicate PMP activity include CEA, CA-125, and CA 19-9. 

Unfortunately, tumor markers are not accurate indicators for everyone. Some patients will have no elevation in their tumor markers despite having an extensive, aggressive tumor.

Imaging

Imaging scans may be able to detect the presence of PMP in the abdomen, including :

  • Computed tomography (CT) scan: A CT scan takes pictures of the inside of the body using X-rays taken from different angles. A computer combines these pictures into a detailed, three-dimensional image that shows any abnormalities or tumors. A CT scan can be used to measure the tumor’s size and how far it has spread.
  • Magnetic resonance imaging (MRI): There is a growing interest in the use of MRI to diagnose appendix cancer and PMP. An MRI uses magnetic fields, not X-rays, to produce detailed images of the body. A special dye called a contrast medium is given before the scan to create a clearer picture.

Differential Diagnosis

Symptoms of the following disorders can be similar to those of PMP and need to be ruled out:

  • A type of ovarian cancer known as low malignant potential ovarian tumor may look similar to PMP.
  • Mucinous cancers of the ovary, colon, stomach, and gallbladder may produce an excess of mucus in the abdominal cavity. These cancers are usually much more aggressive than PMP.
  • Mesothelioma is a rare form of cancer that affects the membrane that covers and protects various internal organs of the body (peritoneum). Mesotheliomas may result in a mucinous tumor within the abdomen that is very difficult to distinguish from PMP.
  • Appendicitis is an inflammation of the appendix. It is characterized by abdominal pain. Pain typically becomes more intense and localizes near the lower right side of the abdomen. Other symptoms of appendicitis may include fever, loss of appetite, vomiting, and tenderness in the abdomen.

Summary

PMP is a very rare manifestation of certain types of cancer that is slow growing and doesn't always show symptoms until it is at an advanced stage.

A doctor may find PMP during tests for another condition, such as surgery to remove the appendix, imaging scans, and blood tests.

A Word From Verywell

If you have a gradually increasing waist size with no obvious cause or swelling, as well as tenderness in your abdomen that doesn't go away, speak to your healthcare provider.

Your doctor will order tests to rule out PMP and find the underlying cause of your symptoms. PMP is rare, so it's likely that your symptoms are a result of something less serious.

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3 Sources
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