What Is Pseudomyxoma Peritonei?

Pseudomyxoma peritonei (PMP) is a rare and indolent (slow-growing) type of abdominal cancer. Around two people per million are diagnosed with PMP each year.

PMP causes a buildup of mucus-secreting (mucinous) tumor cells in the lining of the abdominal cavity (peritoneum) and pelvis. Mucinous tumor cells produce mucus (mucin), which has a jelly-like quality.

PMP tumor cells may spread throughout the abdomen and pelvis. They may also affect the ovaries (egg-producing organs).  

Unlike other cancers, PMP doesn't typically spread to distant sites in the body.

This article will discuss the types, symptoms, causes, diagnosis, and other factors associated with treating PMP.

The abdomen is located between the chest and pelvis. It contains all the organs needed for digestion, including the stomach, large and small intestines, liver, pancreas, and gallbladder. These organs are covered with peritoneal fluid, so they can slide against each other without friction.

The abdomen also houses the spleen and kidneys. Blood vessels, including the aorta, travel through this area of the body.

This article will discuss all aspects of PMP including causes, treatments, diagnosis, and prognosis.

Types of Pseudomyxoma Peritonei

There are three classifications or stages of PMP. These stages are determined by the number of mucinous tumor cells in mucin and how they look under a microscope:

• Low grade mucinous carcinoma peritonei (MCP-1): Low-grade tumor cells which grow and spread slowly
• High grade mucinous carcinoma peritonei (MCP-2): Aggressive, high-grade tumor cells which spread more quickly than low-grade tumor cells
• High grade mucinous carcinoma with signet ring cells (MCP-3): High-grade tumor cells that contain signet ring cells. Signet ring cells are filled with mucin. The mucin displaces the cell’s nucleus, giving it a ring-like appearance.
  

Pseudomyxoma Peritonei Symptoms

PMP is slow-growing, so you may not have symptoms for a long time. As the disease progresses, mucin in your abdomen will become copious. This causes an enlarged abdomen, the most common early symptom of this disease. You may also feel abdominal pressure or discomfort.

Inguinal hernias are a common symptom in people with testes. Inguinal hernia is caused by the protrusion of a part of the intestines through a weak part of the abdominal wall, near the groin.

Abnormally large ovaries, caused by a rapidly growing mucinous tumor in ovarian tissue, is a common finding in people with ovaries.

Causes of Pseudomyxoma Peritonei

Appendix cancer is the most common cause of PMP. There are no known genetic risk factors or environmental causes for this disease.

PMP occurs when a polyp-like growth in the appendix pushes into the peritoneum through the abdominal wall. This growth is called a low-grade appendiceal mucinous neoplasm (LAMN).

Mucinous tumor cells from the appendix slowly migrate throughout the peritoneum and abdominal organs, where they attach themselves and secrete mucin (mucus). The tumor cells may also infiltrate the pelvis. The tumor cells may attach themselves to one or both ovaries, if present.

Diagnosis

Because it’s slow growing, PMP is often suspected during a test or treatment for another condition. If you have symptoms, your healthcare provider will give you a physical examination and several tests to confirm the diagnosis. Tests include:

• Biopsy: A biopsy is required to rule out other conditions and to make a definitive diagnosis of PMP. Abdominal tissue will be removed and examined under a microscope in a laboratory. Based on your symptoms, you may have a fine needle aspiration biopsy done under a local anesthetic, or a laparoscopic biopsy (keyhole surgery) done under general anesthesia.  
• Imaging tests: Imaging tests enable your healthcare provider to view your internal organs. They’re beneficial for making a diagnosis and for determining disease spread. Imaging tests for PMP include computed tomography (CT) scans, magnetic resonance imaging (MRI) tests, and ultrasounds. In people with ovaries, an internal transvaginal ultrasound may be done to look for evidence of PMP in the ovaries.
• Blood tests: Blood tests are done to check for elevated tumor marker levels. Carcinoembryonic antigen (CEA) is a tumor marker associated with gastrointestinal cancers. CA-125 is a tumor marker that indicates mucin production. CA 19-1 is a protein produced by PMP cancer cells and other abdominal cancer cells. 

Treatment

Treatments for PMP are done to eradicate or slow down the progression of the disease. They are also used to alleviate symptoms. The extent of spread and your overall health will be considered when your treatment plan is designed.

If the disease is not causing symptoms, your healthcare provider will recommend watchful waiting. You will be monitored to check for tumor growth or spread during this time.

The most common and aggressive form of treatment is cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (HIPEC). Cytoreductive surgery removes mucin and mucinous tumors from the abdomen and pelvis. The original appendiceal tumor will also be removed. Abdominal organs may be removed in some instances.

This surgery may last for 10 hours or longer. After surgery, while you are still under anesthesia, a heated chemotherapy liquid will be placed into your abdomen to kill any remaining cancer cells. This portion of the procedure is called hyperthermic intraperitoneal chemotherapy. HIPEC may be repeated several times over the next few days.

If you are not a candidate for cytoreductive surgery, debulking surgery, either with or without HIPEC, may be recommended. Debulking surgery removes mucin and PMP cancer cells. It is beneficial for reducing the spread and alleviating symptoms.

If you are not a candidate for either surgery, chemotherapy may be recommended. Chemotherapy is beneficial for slowing down or stopping cancer spread and alleviating symptoms.  

Prognosis

Since PMP is slow-growing, you may have many symptom-free years before you require treatment. Once treatment takes place, PMP is cured in around 65% of patients. Your prognosis will be determined largely by the extent of disease spread and your ability to undergo aggressive treatment.

Coping

It can be upsetting to find out you have a rare cancer. The treatments for PMP can be physically and mentally challenging, making it even harder to cope. As with so many things in life, your journey may be easier if you reach out to others for support.

There is no one-size-fits-all strategy for getting the help you need. You may be able to get support from loved ones and friends. Or, you may benefit from seeing a therapist who specializes in the needs of people living with cancer. If you're on Facebook, there are several PMP support groups you may wish to join.

Coping with any type of cancer is also easier if you practice self-care. Anxiety-busters vary from person to person but may include exercise, meditation, and yoga. Eating healthy food and participating in activities you enjoy are also beneficial.

Summary

Pseudomyxoma peritonei is a rare form of abdominal cancer that usually originates in the appendix. PMP is earmarked by the abundant production of mucin by mucinous cancer cells in the abdomen and pelvis. Treatments for PMP can be aggressive, but yield a cure rate of around 65%.

A Word From Verywell

PMP is often curable. Since it's so rare, there's no screening test for this condition. If you have PMP symptoms, talk to your healthcare provider about testing that can confirm a diagnosis or rule it out.

If you have PMP, you're not alone. Creating a support system of others with PMP or with other types of cancer can help you find the strength and inspiration you need to get through.