Causes of Pseudomyxoma Peritonei

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Pseudomyxoma peritonei (PMP) is a very rare, slow-growing type of abdominal cancer. It has no known genetic, hereditary, or environmental risk factors. Estimates about the frequency of this disease vary. Approximately three people per million are diagnosed annually with PMP.

PMP is characterized by an accumulation of mucin in the lining of the abdominal cavity (peritoneum). Mucin is a component of mucus that has a jelly-like consistency. The peritoneum is the lining that covers the wall of the abdomen as well as most of the organs in the abdominal cavity.

This article will discuss the most common causes and pathways of pseudomyxoma peritonei.

Appendix

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Common Causes

The most common cause of pseudomyxoma peritonei is appendix cancer. The appendix is a small, hollow, cylindrical structure attached to the lower right part of the large intestine (colon). Its function is unclear.

PMP occurs when tumors in the appendix that secrete mucus (mucinous tumors) burst through the wall of the appendix and leak into the abdominal cavity. There, the tumor cells implant themselves inside the peritoneum or abdominal organs and continue to produce mucin.

The tumors that cause PMP can be malignant (cancerous). Adenocarcinomas, which start in gland-forming cells, may result in PMP. However, benign tumors (polyps) can also cause this disease. These are known as low-grade mucinous neoplasms of the appendix.

While less common, mucinous tumors from other areas of the body can also cause PMP. They include:

  • Bladder (the organ that stores urine before voiding)
  • Ovaries (the organs that produce eggs)
  • Colon (the large intestine, which digests and absorbs nutrients)
  • Stomach (the organ where digestion of food begins)
  • Pancreas (the organ that produces digestive enzymes to break down food and hormones, including insulin and glucagon that regulate blood sugar)

How Does Pseudomyxoma Peritonei Spread?

Unlike most cancers, PMP does not usually infiltrate the blood or lymphatic system to travel to other parts of the body. Instead, it confines itself to the abdomen, where it grows slowly and spreads through the peritoneal fluid.

Peritoneal fluid covers the organs within the abdomen. It provides lubrication that reduces organ friction during digestion and bodily movements. PMP tumor cells spread by following the current of peritoneal fluid as it flows throughout the abdomen and pelvis.

Common areas where PMP tumor cells may adhere and grow include:

  • Greater omentum (a four-layer fold of peritoneum that extends from the stomach to the transverse colon)
  • Below the diaphragm (the muscle that separates the abdomen from the chest)
  • Within the pelvis (the abdominal area between the hip bones)
  • On the ovaries

Genetics and Risk Factors

No genetic or environmental risk factors have as yet been identified for this condition. Pseudomyxoma peritonei does not run in families.

It’s not linked to any one ethnicity or sex, either. At one time it was thought that PMP was more likely to occur in females than in males, but this has been disproven.

Pseudomyxoma peritonei affects younger people than other abdominal cancers. The average age at the point of diagnosis is 48.

Summary

Pseudomyxoma peritonei (PMP) is a very rare, slow-growing type of abdominal cancer. It is earmarked by the presence of mucin in the abdominal cavity. PMP is diagnosed in approximately three out of 1 million people annually.

PMP tumor cells usually remain contained within the abdomen and pelvis. Unlike other cancers, pseudomyxoma peritonei does not typically spread (metastasize) to distant areas of the body.

The most common cause of pseudomyxoma peritonei is infiltration into the peritoneum of benign or malignant tumor cells from the appendix (appendix cancer). It can also be caused by malignant or benign tumors from other parts of the body.

There are no known genetic, familial, or environmental risk factors for this disease.

A Word From Verywell

If you have been diagnosed with pseudomyxoma peritonei, you may wonder why it happened to you. Take some comfort in knowing that nothing you did caused it.

Because it is a rare condition, it may be harder to find information about or connect with other people with PMP, and this can be frustrating. Try to remember that the goal of PMP treatment is a cure. There is reason to have high hopes that you will conquer pseudomyxoma peritonei. 

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4 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. National Organization for Rare Disorders. Pseudomyxoma peritonei

  2. Patrick-Brown TDJH, Carr NJ, Swanson DM, Larsen S, Mohamed F, Flatmark K. Estimating the prevalence of pseudomyxoma peritonei in europe using a novel statistical method. Ann Surg Oncol. 2021;28(1):252-257.

  3. ACPMP Appendix Cancer Pseudomyxoma Peritonei Research Foundation. About appendix cancer.

  4. Cancer Research UK. About pseudomyxoma peritonei.