Pseudomyxoma Peritonei

Pseudomyxoma peritonei is a very rare cancer that fills the abdomen with a jelly-like substance. It usually begins in the appendix and slowly spreads within the belly, earning it the nickname “jelly belly.” Though challenging to diagnose early, modern treatments combining surgery and chemotherapy can offer hope for long-term survival.

Table of contents

• What is pseudomyxoma peritonei?
• Identification codes and synonyms
• Associated anatomy
• Symptoms
• Causes and risk factors
• How pseudomyxoma peritonei spreads
• Diagnosis
• Treatment
• Prognosis
• Living with pseudomyxoma peritonei

What is pseudomyxoma peritonei?

Pseudomyxoma peritonei (PMP) is a very rare cancer that affects the space inside your abdomen. The name literally means “false mucinous tumor of the peritoneum”^[1]. This condition is characterized by the buildup of mucin, a jelly-like substance that is one of the components of mucus, within the abdominal cavity^[1].

PMP is extremely rare, affecting only between 1 and 4 people per 1 million each year^[1][2]. Women are affected more frequently than men, with patients having an average age of 53 years at the time of diagnosis^[2].

The disease typically begins as a small growth called a polyp in the appendix. This polyp is different from polyps that cause bowel cancer^[3]. The growth is called a Low Grade Appendiceal Mucinous Neoplasm (LAMN)^[3]. When this polyp breaks through the appendix, it triggers a flood of mucin-producing cancer cells that spread throughout the abdominal cavity^[1].

Healthcare providers call this disease a “false tumor” because the cancer doesn’t form a tumor that can spread through the bloodstream or lymphatic system like most cancers do. Instead, it spreads by producing large amounts of jelly-like mucin inside the belly, which is why some people call PMP “jelly belly”^[1][3].

PMP is often considered a borderline malignant condition because, although it doesn’t spread to other parts of the body through typical cancer pathways, it does grow and spread inside the abdomen^[3][10].

Identification codes and synonyms

jelly belly, LAMN (Low Grade Appendiceal Mucinous Neoplasm), disseminated peritoneal adenomucinosis (DPAM), peritoneal mucinous carcinomatosis (PMCA)

Associated anatomy

• Appendix
• Peritoneum
• Peritoneal cavity
• Abdominal organs (digestive system)
• Ovaries (in some cases)

The peritoneum is a sheet of tissue that covers the organs inside your abdomen. It has two layers: the parietal layer lines the abdominal wall, and the visceral layer covers the organs. The space between these layers is called the peritoneal space^[3]. The peritoneum also makes a lubricating fluid called peritoneal fluid that helps the organs move smoothly against each other as you move around^[3].

Symptoms

Pseudomyxoma peritonei symptoms develop very slowly, and you may not notice them at first or may assume they are from a common illness^[1]. Many people don’t have any symptoms until their bellies are filled with mucin^[1]. It might be years before you have any symptoms of this type of cancer^[3].

Some people won’t have any symptoms at all, which makes PMP difficult to diagnose. Sometimes, healthcare providers detect PMP early on while doing an annual exam or while checking for another medical condition^[1][3].

Common symptoms may include^[1][3]:

• Abdominal distension (swollen abdomen): This is when your abdomen is noticeably swollen
• Abdominal pain: This may feel like general discomfort or pain as mucin builds up in your belly
• Swelling and bloating in your abdomen
• Constipation: Abdominal swelling may block your large intestine so you can’t pass stool
• Changes in bowel habits
• Difficulty getting pregnant: Pressure from mucin buildup or inflammation in your reproductive organs can make it difficult to conceive, especially for women
• Hernias: Mucin buildup may push one of your organs through a gap in your muscle wall. Inguinal hernia is one of the most common PMP signs in men
• Loss of appetite
• Feeling of fullness
• Nausea

In women, PMP can sometimes be confused with ovarian cancer because ovarian cancer may also cause a swollen abdomen, and some types of ovarian cancer cells also produce mucin^[3].

Causes and risk factors

Experts aren’t sure what causes the chain of events that leads to pseudomyxoma peritonei^[1]. We don’t know what causes this type of cancer, though most cancers are caused by a number of different factors working together^[3].

The primary tumor appears to arise from goblet cells that express a protein called MUC2, most commonly in the appendix. The KRAS and p53 genes may be involved in the development of the cancer^[5].

Patients with familial adenomatous polyposis (FAP) demonstrate an increased risk of developing mucinous adenocarcinoma of the appendix. KRAS mutation has also been present in 70% of appendiceal adenomas^[2].

While the majority of cases are associated with appendiceal cancer, other primary sites have been reported, including the colon, rectum, stomach, gallbladder, bile ducts, small intestine, urinary bladder, lung, breast, fallopian tubes, pancreas, and ovaries^[5]. However, in most cases where ovaries appear to be involved, this is actually a spread from an appendiceal or other gastrointestinal source^[5].

How pseudomyxoma peritonei spreads

Pseudomyxoma peritonei doesn’t behave like most cancers. It rarely spreads through the bloodstream or the lymphatic system to other parts of the body. Instead, it spreads inside the abdomen^[3].

There are several steps involved in how PMP develops. Initially, tumor cells originating from the mucinous lining of the appendix continuously produce mucus into the appendiceal opening and form a mucocele, which eventually ruptures^[2].

Free-floating mucinous tumor cells then move to various parts of the peritoneal cavity following the intraperitoneal fluid current and gravity. This is called the “redistribution phenomenon”^[2]. The cancer cells generally spread by following the flow of peritoneal fluid^[3].

The intraperitoneal fluid is most frequently reabsorbed through the right side of the abdomen toward the right diaphragm and the omentum (fatty layers in the abdomen), making these the major sites of tumor deposits when cells get trapped in small lymphatic systems^[2]. The cells attach to the peritoneum at particular sites and produce mucus which collects inside the abdomen and eventually causes symptoms^[3].

Without treatment, the mucin will fill the abdominal cavity, pressing on the bowel and other organs. This can result in compression of organs and destroy the function of the colon, small intestine, stomach, or other organs^[5].

Diagnosis

It can be difficult to diagnose PMP. Doctors sometimes find it by accident during treatment for other conditions^[3]. This disease is often discovered during surgery for other conditions, such as hernia repair^[5].

A healthcare provider will ask questions about your symptoms, like when you first noticed them or if they’re getting worse. They’ll do a physical examination and order blood tests and imaging tests^[1].

Blood tests

A provider may order a complete blood count (CBC) and blood tests to look for tumor markers. Tumor markers are substances in your body that may indicate signs of cancer^[1].

Imaging tests

Your provider may order the following imaging tests to look for issues like enlarged organs, fluid buildup in your abdomen (ascites) or mucin deposits in your belly (jelly belly)^[1][3]:

• Ultrasound scan: This uses sound waves to make a picture
• CT scan (computed tomography): This takes a number of X-rays from different angles and puts them together to give more detailed information
• MRI (magnetic resonance imaging): This uses powerful magnets and radio waves to make detailed images

A provider may also do a needle biopsy to get fluid or tissue from your peritoneum. A medical pathologist will examine fluid or tissue cells under a microscope^[1].

A provider may also do a laparoscopy to look at the inside of your belly or to take tissue samples for analysis. Often, doctors can only diagnose pseudomyxoma peritonei properly after an operation to look into the abdomen, called a laparotomy^[1][3].

In most cases, a colonoscopy is unsuitable as a diagnostic tool because, in most cases, appendix cancer invades the abdominal cavity but not the colon^[5].

Treatment

The main treatments for pseudomyxoma peritonei are surgery and chemotherapy together^[11]. Treatment will depend on your situation, including where the cancer is, the extent of disease, and your general health^[3].

Complete cytoreductive surgery (CRS) followed by hyperthermic intraperitoneal chemotherapy (HIPEC) is currently the standard of care for pseudomyxoma peritonei^[9]. This combined approach has been established and proved to be an effective treatment for PMP^[15].

Watch and wait

You might not start treatment straight away. As PMP is a slow developing tumor, your doctor may recommend watchful waiting if the cancer is small and slow growing and you don’t currently need treatment^[11][14].

Your doctor will check up on you regularly with blood tests and scans. This approach is also sometimes called active surveillance^[11]. You might find it hard to cope with this and struggle with feeling that no action is being taken^[11].

Cytoreductive surgery with HIPEC

Where possible, you’ll have surgery combined with chemotherapy. The aim is to remove all of the visible PMP cells in your abdomen so there will be no cancer cells left that could start to grow again^[11].

The surgery involves the surgeon removing any tissue affected by PMP. The surgeon strips out the lining of the abdomen (the peritoneum). The operation varies between people, but can include removing^[11]:

• Part of the bowel
• The spleen
• Cancer attached to the surface of the liver
• The fatty layers in the abdomen (the omentum)
• The gallbladder
• The lowest part of your bowel (rectum)
• The womb and ovaries if you are a woman
• The bellybutton
• The affected lining of your abdomen (peritoneum)

If the surgeon removes your spleen, you might need to have some vaccinations before or just after the operation, and you will need to take antibiotics for the rest of your life because of changes to your immune system^[11].

During your operation, the surgeon puts heated chemotherapy directly into the peritoneal space inside your abdomen. This is called hyperthermic intraperitoneal chemotherapy, or HIPEC^[11]. The aim is to kill any PMP cells that remain in the abdomen. Heating the chemotherapy can improve how well it works^[11].

You usually have a chemotherapy drug called mitomycin C. You sometimes have other drugs, such as oxaliplatin^[11].

This is major surgery. The operation can take around 10 hours and your recovery can be slow^[11]. Sometimes people need more than one operation, several months apart^[11].

After surgery

You might be in intensive care or a high dependency unit for 24 to 48 hours. You might also have a catheter (tube in the bladder), an epidural (tube in the spine for pain relief), a nasogastric tube (tube down your nose into your stomach to stop you being sick), drains in the tummy, and feeding through a drip into a vein for about 2 weeks^[11].

You’re likely to be in hospital for 2 to 3 weeks. Some people may also need a blood transfusion after the operation^[11]. It takes a long time to recover from this operation. It can be at least 6 months before you are fully active again and able to work^[11].

Other treatment options

If you can’t have cytoreductive surgery, your doctor may suggest^[11]:

• Debulking surgery: This removes as much cancer as possible. It won’t cure PMP, but it can help you feel better. Even if complete cytoreductive surgery is not feasible, debulking could improve quality of life and prolong survival^[9].
• Chemotherapy: If you can’t have cytoreductive surgery, the doctor may suggest you have chemotherapy. The drugs may be given through your veins^[7].

Prognosis

Prognosis with treatment in many cases is optimistic, but the disease is lethal if untreated, with death occurring via wasting away (cachexia), bowel obstruction, or other types of complications^[5].

The grade of the primitive tumor and its peritoneal extension are prognostic factors in PMP of appendiceal origin and determine the therapeutic strategy^[9].

With effective treatment options available, the natural history of this disease has been drastically modified since the introduction of the peritonectomy procedure^[10]. However, some patients may require repeated surgeries over an extended period^[19].

Living with pseudomyxoma peritonei

Recovery from PMP treatment can be challenging and lengthy. Many patients describe their experience as “the struggle of a lifetime,” but with modern treatment approaches, there is hope for a cure^[19].

After treatment, you will need regular follow-up care. Some patients need to undergo scans for extended periods—sometimes up to 20 years—to monitor for any recurrence of the disease^[20].

Because PMP is so rare, it is important to seek care from specialists experienced in treating this condition. Optimal management demands a multidisciplinary approach^[19]. Expertise and multicentric cooperation are needed to improve outcomes for patients^[9].

Support from patient organizations and connecting with others who have experienced PMP can be valuable during your journey. Many patients find that sharing their stories and connecting with fellow patients helps them cope with the challenges of this rare disease^[20].