Written By: Camryn Keeble

Peritoneal Mesothelioma Diagnosis

A peritoneal mesothelioma diagnosis is the first step towards receiving treatment and killing this cancer. To ensure a proper diagnosis, patients should seek out a mesothelioma specialist – a doctor specifically experienced with treating mesothelioma. There are steps doctors must follow when diagnosing peritoneal mesothelioma.

Karen Ritter, RN BSN

Medically Reviewed By

Karen Ritter, RN BSN

Registered Nurse


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Important Facts About How Peritoneal Mesothelioma Is Diagnosed

  • Diagnosing peritoneal mesothelioma may include imaging tests, such as X-rays, CT scans, PET scans or MRIs.
  • The only way to get a definitive peritoneal mesothelioma diagnosis is with a tissue biopsy.
  • Doctors often use a systematic approach to finding a mesothelioma diagnosis called a differential diagnosis. It involves compiling a list of conditions with similar symptoms.

How Is Peritoneal Mesothelioma Diagnosed?

Diagnosing peritoneal mesothelioma can be challenging due to the similarity between mesothelioma symptoms and other common conditions. The only way to get a proper diagnosis is to undergo a peritoneal mesothelioma diagnosis test, or tissue biopsy.

There are a few ways to detect peritoneal mesothelioma, but the most effective method for diagnosis is a tissue biopsy. During a peritoneal mesothelioma tissue biopsy, doctors remove a sample of peritoneal tissue and send it to a pathologist for assessment.

Mesothelioma specialists use a laparoscope to obtain a biopsy. Surgeons will make a small incision in the abdomen and use a microscopic camera to explore the abdominal cavity. The tiny camera also contains a tool to help remove tissue for a peritoneal mesothelioma biopsy. Other methods to detect peritoneal mesothelioma are via X-rays and CT scans. The patient may also undergo a PET scan or MRI.

What Is the Peritoneum?

The peritoneum is the lining of the abdominal cavity where peritoneal mesothelioma forms. This very thin lining is made of tissue layers and fluid and allows for the passage of nerves, blood vessels and lymphatic fluids.

The peritoneum is made of two layers – the parietal peritoneum and the visceral peritoneum. The space between the layers (peritoneal cavity) contains fluid and protects the abdominal organs, such as the intestines, spleen, liver and more.

The cells in the peritoneum are called mesothelial cells. The peritoneum, also called the mesothelium, protects, lubricates, provides structure to the organs in the abdomen and helps in the immunity process.

Peritoneal Mesothelioma Differential Diagnosis

The difficulty in diagnosing mesothelioma is it can display vague symptoms that can be associated with many other common health conditions. Doctors often create a list of possible causes and related diseases based on the patient’s symptoms. This list is the mesothelioma differential diagnosis, and it helps doctors determine which tests to perform.

The steps used for a peritoneal mesothelioma diagnosis and additional testing methods should help separate mesothelioma from other conditions.

Some conditions doctors may consider in the differential diagnosis of peritoneal mesothelioma are:

  • Peritoneal carcinomatosis
  • Serous peritoneal carcinoma
  • Ovarian carcinoma
  • Lymphomatosis
  • Tuberculous peritonitis

Steps to Get a Peritoneal Mesothelioma Diagnosis

The steps to getting a proper peritoneal mesothelioma diagnosis involve recognizing the symptoms of peritoneal mesothelioma, visiting a doctor and undergoing various testing. The steps can change depending on the patient’s circumstances, but the typical steps of getting a peritoneal mesothelioma diagnosis often include the following:


Meet with your primary physician to discuss symptoms.


Get an abdominal X-ray to look for abnormalities.


Get a computed tomography (CT) scan for a three-dimensional view of your abdominal cavity.


Get a biopsy to test tissue samples.

Peritoneal Mesothelioma Diagnosis Testing

Patients may undergo different types of imaging scans and biopsy tests as part of peritoneal mesothelioma diagnosis testing, such as:

  • X-ray – Provides a two-dimensional image to show any signs of a tumor, mass or fluid buildup in the abdomen
  • CT scan – Provides three-dimensional images of the abdominal cavity and peritoneum
  • PET scan – Sends radioactive sugar into the blood for cancerous cells to absorb while a special camera sends a picture of the radioactive energy back to the medical team for real-time footage
  • MRI scan – Creates detailed images of soft tissue to help locate any abnormalities or tumors
  • Biopsy – Removes a tissue or fluid sample from the peritoneal cavity to examine under a microscope. A tissue biopsy is the only way to get a definitive diagnosis of peritoneal mesothelioma

Types of Biopsies for Peritoneal Mesothelioma Diagnosis

There are a couple different types of biopsies used to diagnose peritoneal mesothelioma. These biopsies are split into two groups: tissue biopsies and fluid biopsies. Tissue biopsies are the only way to get a true diagnosis of mesothelioma but require a slightly more invasive approach.

The procedures used to obtain tissue biopsies for a peritoneal mesothelioma diagnosis are:

  • CT-guided core-needle biopsy – Doctors use a CT scan to guide the surgeon to the correct area of the body then a needle is inserted through the skin to retrieve tissue samples (biopsies).
  • Diagnostic laparoscopy Doctors make a small incision in the abdomen and use a small camera and instruments to examine the peritoneal cavity, assess the organs in the abdomen and take tissue samples (biopsies) to confirm a peritoneal mesothelioma diagnosis.

Non-surgical biopsies, also called mesothelioma peritoneal fluid analysis, use a needle and syringe to remove fluid from the abdominal cavity to test for peritoneal mesothelioma cancer cells.

Diagnosing the Peritoneal Mesothelioma Stages Using the Peritoneal Cancer Index

An essential part of a peritoneal mesothelioma diagnosis is determining the stage of the cancer, as it heavily affects the prognosis and treatment options. The difference between peritoneal mesothelioma and most cancers is the staging system used. The Peritoneal Cancer Index is used to stage peritoneal cancer, like peritoneal mesothelioma.

The Peritoneal Cancer Index assigns scores to 13 separate sections of the abdominal cavity. Each section receives a score between 0 and 3, depending on the size and number of tumors in the space. A score of 0 means there is no cancer, while a score of 3 means cancer has filled the area. The scores are totalled and assigned to a stage: stage 1 (PCI 1-10), stage 2 (PCI 11-20), stage 3 (PCI 21-30) and stage 4 (PCI 31 and higher).

Frequently Asked Questions About Peritoneal Mesothelioma Diagnosis

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What Are the Tests for a Peritoneal Mesothelioma Diagnosis?

The main tests used for a peritoneal mesothelioma diagnosis are imaging scans and a tissue biopsy. People who suspect they may have peritoneal mesothelioma cancer need to see their doctor for an in-depth evaluation, abdominal X-ray, followed by a CT scan and an MRI scan, if necessary. If there are abnormalities found to suspect mesothelioma, then doctors will recommend a tissue biopsy. These are the typical steps to peritoneal mesothelioma diagnosis testing.

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What Biopsies Are Used for a Peritoneal Mesothelioma Diagnosis?

The two tissue biopsy procedures used for a peritoneal mesothelioma diagnosis are a CT-guided core-needle biopsy and a laparoscopy. These all require an incision to the patient’s abdomen and removing a tissue sample to test for peritoneal mesothelioma. Another biopsy technique removes fluid from the abdomen for a mesothelioma peritoneal fluid analysis, which is typically less conclusive than a tissue biopsy.

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Are Mesothelial Cells Normal in Peritoneal Fluid?

Yes, mesothelial cells are normal in peritoneal fluid. The peritoneum is the thin lining of the abdominal cavity where peritoneal mesothelioma forms. This very thin lining is made of tissue and fluid and allows for the passage of nerves, blood vessels and lymphatic fluids The peritoneum has two tissue linings, which are made of mesothelial cells. In between the tissue linings is fluid (peritoneal fluid), so it’s normal for mesothelial cells to be found in peritoneal fluid.

Sources & Author

    1. Anatomy, Abdomen and Pelvis, Peritoneum. National Library of Medicine. Retrieved from: https://www.ncbi.nlm.nih.gov/books/NBK534788/. Accessed: 03/27/2023.
    2. Malignant peritoneal mesothelioma: a review. National Library of Medicine. Retrieved from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5497105/. Accessed: 03/28/2023.
    3. Peritoneal biopsy. Macmillan Cancer Support. Retrieved from: https://www.macmillan.org.uk/cancer-information-and-support/diagnostic-tests/peritoneal-biopsy. Accessed: 03/28/2023.
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About the Writer, Camryn Keeble

Camryn Keeble is the senior content writer and editor for Mesothelioma Guide. She creates informative content to educate mesothelioma patients and their loved ones on news, treatments and more. She also works diligently to raise awareness of the dangers of asbestos exposure and the effects of mesothelioma.