Peritoneal Mesothelioma

May 1, 2025

This page was reviewed under our medical and editorial policy by Mustafa Raoof, M.D., assistant professor, Division of Surgical Oncology, Department of Surgery, City of Hope^® Cancer Center Duarte

Peritoneal mesothelioma is a rare, aggressive form of cancer affecting the peritoneum, a membrane lining the abdominal cavity and organs. Asbestos is a risk factor for developing both peritoneal mesothelioma and pleural mesothelioma, which is more common. Both types are typically malignant (cancerous).

What Is Peritoneal Mesothelioma?

Though peritoneal mesothelioma is the second most common type of mesothelioma, it is still rare, accounting for just 10% to 30% of all mesothelioma cases. In the United States, this translates to as few as 300 to 500 diagnoses each year, mostly among people in their 50s. The disease is more common among women.

As its name suggests, peritoneal mesothelioma forms in the peritoneum, a membrane lining the abdominal cavity and covering abdominal organs like the stomach, liver, kidneys, bladder and intestines. It is difficult to detect early, often spreading throughout the abdominal lining before diagnosis.

Peritoneal Mesothelioma Causes and Risk Factors

Mesothelioma and asbestos often go hand-in-hand. That’s because exposure to asbestos, a mineral fiber naturally present underground in rock and soil, is the leading risk for pleural mesothelioma, which develops in the lining of the lungs.

The connection between asbestos and peritoneal mesothelioma is less understood. Many individuals diagnosed with the disease don’t work in professions — like construction, electrical work, manufacturing and the automotive industry — that expose them to asbestos. In fact, asbestos is only linked to approximately 30% to 50% of peritoneal mesothelioma cases.

In addition to asbestos exposure, other risk factors for developing peritoneal mesothelioma include:

• Exposure to silica and erionite exposure, common minerals in the earth
• Exposure to radiation through radiation therapy to treat abdominal cancer
• Specific gene mutations, most commonly a change affecting the BAP1 gene, in combination with asbestos exposure

Peritoneal Mesothelioma Symptoms

Many patients don’t experience symptoms until peritoneal mesothelioma has spread to organs in the abdominal cavity. The most common symptom is fluid buildup in the abdomen.

Other signs of peritoneal mesothelioma include:

• Abdominal swelling, bulging or pain
• A painful mass in the pelvic area
• Nausea and vomiting
• Constipation or bowel blockage
• Unexplained fever
• Unexplained weight loss
• Loss of appetite

Diagnosis and Testing

Peritoneal mesothelioma may be difficult to distinguish from gastrointestinal cancers, ovarian cancer and irritable bowel syndrome (IBS). That’s why doctors may use a variety of tools to rule out these more common conditions and accurately diagnose peritoneal mesothelioma, including those listed below.

Imaging tests: Such tests — such as computed tomography (CT) scan or magnetic resonance imaging (MRI) — to see tumor location and size

Blood tests: These are performed to check for markers, such as certain proteins, in the blood that may signal a tumor

Peritoneal fluid analysis: This is a procedure involving collection of fluid to test for evidence of mesothelioma

CT-guided core needle biopsy or laparoscopic biopsy: In these procedures, doctors remove a tumor sample from the abdominal lining for lab examination and testing to confirm a peritoneal mesothelioma diagnosis

Peritoneal Mesothelioma Stages

Evaluating how much cancer there is and where it has spread is called staging, an important step in determining treatment options and prognosis.

In cases where doctors move forward with staging peritoneal mesothelioma, they may utilize the peritoneal cancer index (PCI).

The system works by segmenting the abdominal region into 13 distinct sections, then assigning a number from 0 to 3 to each section (zero means no cancer; 3 means cancer has inundated an area). The care team adds the numbers for each section to establish the cancer stage, with stage 1 as least advanced and stage 4 as most advanced, as detailed below.

Stage 1: PCI score from 1 to 10.

Stage 2: PCI score from 11 to 20.

Stage 3: PCI score from 21 to 30.

Stage 4: PCI score from 31 to 39.

The physician may use a different staging method for peritoneal mesothelioma, so always ask for specifics about the patient’s stage, and what it means, depending on the patient’s specific situation.

Peritoneal Mesothelioma Treatment

Factors like tumor location and stage, as well as a patient’s overall health, influence personalized treatment plans, but the most common treatment for peritoneal mesothelioma is cytoreduction surgery with hyperthermic intraoperative peritoneal perfusion with chemotherapy (HIPEC).

Surgery

During cytoreduction, or cytoreductive surgery, a surgeon removes tumors from the abdomen and parts of the membrane lining the abdominal cavity and abdominal organs where the cancer has spread.

Many eligible patients undergo cytoreduction, followed by HIPEC (short for hyperthermic intraperitoneal chemotherapy) a time-intensive procedure where heated chemotherapy is administered directly into the patient’s abdominal cavity.

Notably, HIPEC is a type of chemotherapy given after cytoreductive surgery. During HIPEC, doctors heat chemotherapy drugs to make them stronger than standard chemotherapy. Once the drugs reach a safe temperature, they are pumped directly into the abdominal cavity, killing any cancer cells missed during surgery.

Chemotherapy

For patients who are unable to undergo cytoreduction with HIPEC, chemotherapy may be an option. These drugs navigate through the bloodstream and destroy cancer cells. Systemic chemotherapy is used much less often than HIPEC for peritoneal mesothelioma.

Medications

Immunotherapy and targeted therapy may also be used in treating peritoneal mesothelioma.

For example, immunotherapy drugs called immune checkpoint inhibitors help the immune system pinpoint and kill cancer cells, whereas targeted therapies seek out genetic changes that turn healthy cells into cancer cells. These may be recommended if surgery isn't an option.

Palliative Care

When it comes to quality of life, palliative care is an important consideration to help manage cancer symptoms and ease treatment side effects. Different procedures may be indicated to help alleviate symptoms.

Fluid buildup in the abdominal cavity (ascites): Some patients with peritoneal mesothelioma gain relief from paracentesis, a procedure that relieves pressure by draining fluid buildup from the abdomen.

Bowel obstruction: Some patients benefit from bowel resection and reconnection. If this is not feasible, sometimes surgeons will bypass the area of blockage so patients can eat normally. In some instances, an ostomy bag is necessary to divert the stool. If these procedures are not possible due to extensive involvement of disease, a tube in the stomach (gastrostomy) can be placed to decompress the stomach and intestines and minimize discomfort and vomiting

Ureter blockage: Some patients will have blockage of ureters by the tumor. The ureters are tubes that connect the kidney to the bladder and transfer urine. Blockage can cause the urine to build up in the kidney and can also cause injury to the kidney. Doctors can place a stent in the ureter to bypass the blockage or sometimes a tube is placed in the kidney to decompress the blockage.

Who Treats Peritoneal Mesothelioma?

Finding specialized care is critical with cancer as rare and aggressive as peritoneal mesothelioma. A patient’s team of multidisciplinary experts may include:

• Medical oncologists, who treat cancer with chemotherapy and other drugs
• Surgical oncologists, who diagnose and treat cancer with surgery
• Gastroenterologists, who specialize in treating digestive system diseases
• Pathologists, who examine tissue samples for diagnostic purposes to help determine a treatment plan
• Radiologists, who utilize imaging tools and interventional techniques to diagnose and treat cancer
• Supportive care providers, who focus on cancer- and treatment-related side effects and symptom management

Peritoneal Mesothelioma Life Expectancy

Due to improved diagnostic technology and treatment breakthroughs, peritoneal mesothelioma has a more favorable prognosis compared to pleural mesothelioma.

One study published in 2020 found that with cytoreductive surgery and HIPEC, median overall survival for peritoneal mesothelioma patients ranged from 22 months to 53 months. It’s important to understand that prognosis depends on various factors, such as tumor stage and tumor removal. Early detection and treatment, as well as successful removal of all tumors by a skilled team, are linked to more positive outcomes.

Patients should talk to their care team to get a prognosis that’s tailored to the patient’s cancer stage, other health conditions and additional factors.