Types of Mesothelioma

There are four types of mesothelioma: Pleural (lungs), peritoneal (abdomen), pericardial (heart) and testicular. Pleural and peritoneal are the most common types, comprising nearly 90 percent of all diagnoses. Learn more about your specific type and what it means for your treatment options.

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Medical experts acknowledge four main types of mesothelioma — each named for the area of the body where the cancer forms. The most common type, pleural mesothelioma, develops in the lining of the lungs.

Peritoneal mesothelioma forms in the peritoneum, the membrane that lines the abdominal cavity. This is the second-most prevalent type. The overwhelming majority of mesothelioma specialists treat patients with one of these two types.

The rarest forms of the disease are pericardial and testicular mesothelioma. Pericardial mesothelioma starts in the lining of the heart, while testicular mesothelioma develops in the lining of the testicles. Together, these types account for less than 2 percent of all mesothelioma diagnoses.

Primary Cause of All Mesothelioma Types

All the different types and subtypes of this disease share one common thread. They are caused primarily by a prolonged exposure to asbestos, usually in the workplace. If a doctor suspects that you have any form of mesothelioma, you should think back through your work background to find a connection to when you worked with or around asbestos materials and products.

Most pleural mesothelioma patients can remember a time when they breathed in asbestos fibers. In cases of peritoneal mesothelioma, patients often swallowed the fibers. Researchers are less certain about how asbestos triggers the pericardial and testicular forms of the disease.

  • Pleural Mesothelioma

    Pleural mesothelioma develops in the mesothelial lining of the lungs, known as the pleura. This type represents approximately 75 percent of all mesothelioma cases. Although symptoms may vary, the most common pleural mesothelioma symptoms include:

    Lungs Icon
    • Shortness of breath
    • Persistent dry cough
    • Persistent chest pain
    • Difficulty swallowing
    • Night sweats / fever
    • Fatigue

    Treatment for pleural mesothelioma largely depends on the stage of the cancer, which doctors use to describe how far it has progressed. When mesothelioma is diagnosed at an early stage, potentially curative surgery may be an option for patients. Most treatments in later stages are palliative, meaning they aim to relieve symptoms and improve quality of life.

    Learn About Pleural Mesothelioma
  • Peritoneal Mesothelioma

    Peritoneal mesothelioma develops in the mesothelial lining of the abdomen, known as the peritoneum. Approximately 20 percent of all mesothelioma cases are peritoneal. Common symptoms of peritoneal mesothelioma include:

    Gastrointestinal icon
    • Abdominal pain
    • Abdominal swelling
    • Weight loss
    • Nausea / vomiting
    • Constipation or diarrhea
    • Fatigue

    Patients with peritoneal mesothelioma may have symptoms caused by thickening of the peritoneal membrane and the build-up of fluid. Because peritoneal mesothelioma spreads throughout the body faster than other types of mesothelioma, treatment may be difficult. Heated chemotherapy has shown promise in treating this type of mesothelioma.

    Learn About Peritoneal Mesothelioma
  • Pericardial Mesothelioma

    Pericardial mesothelioma develops on the exterior lining of the heart, known as the pericardium. This type of mesothelioma is rare and accounts for about 1 percent of all mesothelioma cases. Symptoms develop when fluid builds up in the spaces between the layers of the pericardium. Pericardial mesothelioma symptoms include:

    heart organ icon
    • Irregular Heartbeat
    • Chest Pain
    • Difficulty Breathing
    • Coughing
    • Night Sweats / Fever
    • Fatigue

    As with other types of mesothelioma, doctors most commonly treat pericardial mesothelioma with palliative therapies that relieve symptoms. Removing pericardial tumors with surgery is risky because they grow so close to the heart.

    Learn About Pericardial Mesothelioma
  • Testicular Mesothelioma

    Testicular mesothelioma develops in the tunica vaginalis, the lining of the testes. This is the rarest type of mesothelioma, accounting for less than 1 percent of all cases. Many patients are diagnosed while receiving surgery or treatment for another condition.

    Because of the rarity of this type, it has been difficult for medical researchers to come up with a complete list of symptoms. The two main indicators of this cancer are painless testicular lumps and swelling of the scrotum. This form of mesothelioma is usually not diagnosed until lumps develop.

    Testicular mesothelioma patients may undergo surgery to remove all or part of the affected testicle. Doctors sometimes recommend adjuvant therapy, which involves chemotherapy or radiation therapy after the surgery to kill any remaining cancer cells.

    Learn About Testicular Mesothelioma

How common is each type of mesothelioma?

Percentage of each type of mesothelioma diagram
Mesothelioma body location diagram
  • Pleural Mesothelioma 75% of all cases
  • Pericardial Mesothelioma 1% of all cases
  • Peritoneal Mesothelioma 10-20% of all cases
  • Testicular Mesothelioma < 1% of all cases

It generally isn’t difficult for doctors to discern one type of mesothelioma from another. This is because the cancer grows directly into body structures near where it formed before spreading to other parts of the body. Doctors will clearly see more tumor growth in the chest cavity with pleural mesothelioma, and more tumor growth in the abdominal cavity with peritoneal mesothelioma.

While the same imaging scans and biopsy techniques are used to diagnose all types of mesothelioma, the name and location of the procedure will differ depending upon which type of mesothelioma is suspected. Certain minor surgical procedures that help with mesothelioma diagnosis also vary depending upon the suspected mesothelioma type.

For example, a mediastinoscopy is a minor surgery that takes samples of mediastinal tissue, such as lymph node tissue, to help determine how far pleural mesothelioma tumors have spread in the chest. A paracentesis is a test for peritoneal mesothelioma that extracts fluid from the abdominal cavity so doctors can examine it for signs of cancer.

Doctors consider all forms of mesothelioma to be rare. They also consider all of the types be fast-spreading, which explains why they like to determine the stage of the cancer as soon as possible. The type of cancer affects your treatment options and impacts your life expectancy. Medical research shows that oncologists have more success treating peritoneal mesothelioma than the other three types.

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Malignant vs. Benign Mesothelioma

Most mesothelioma tumors are cancerous, or malignant. Cancerous tumors have an inclination to spread to other locations, intensifying the danger of the cancer.

But not all tumors are malignant. Some turn out to be benign – noncancerous. Benign tumors grow slowly and don’t spread to distant organs. If these tumors grow large enough, they can cause complications that make them necessary to remove, but many people experience no symptoms because of the tumors’ existence.

Benign mesotheliomas usually develop in the abdomen, and they often form in people who have no history of asbestos exposure. Among patients with benign mesotheliomas larger than 7 cm, about 20 percent experience painful swelling of the joints and bones, low blood sugar, comas and seizures. Most people diagnosed with these benign tumors are young to middle-aged women, although doctors have documented benign cases in men.

Benign mesothelioma isn’t typically associated with a history of asbestos exposure. Although it can occur at any age, it is most common among people in their 60s and 70s. Benign mesotheliomas often appear as solitary fibrous tumors that grow as a single mass, while malignant mesotheliomas tend to grow as many small nodules that arise on the mesothelial lining and grow together to form a sheet-like tumor.

A single mass tumor is often easier to remove than a sheet-like tumor, especially if the mass tumor is small. This factor makes benign mesotheliomas easier to remove with surgery. Surgical removal often remedies any symptoms caused by the benign tumor.

The Importance of Cell Type

Another way that doctors can describe a tumor is by examining the type and structure of its cells. Although doctors most commonly classify this cancer based on where the tumor originally formed, there are also various cellular subtypes of pleural, peritoneal, pericardial and testicular mesothelioma.

With the help of histology (the study of microscopic cells), doctors can identify important features of a tumor’s cells and determine the cancer’s histological cell type. This information helps them better predict the cancer’s progression, as well as the patient’s survival time and likely response to treatment.

Most Common Mesothelioma Cell Types

There are three primary mesothelioma cell types: epithelial, sarcomatoid and biphasic.

  • Epithelial Mesothelioma

    Malignant epithelial mesothelioma

    Accounting for 50 to 70 percent of all cases, epithelial mesothelioma is by far the most common histological subtype. Compared with other cell types, epithelial mesothelioma typically responds best to treatment. It is therefore associated with the best survival.

    Papillary mesothelioma, also known as well-differentiated papillary mesothelioma (WDPM), is a rare subtype of epithelial mesothelioma. WDPM is considered a benign type of mesothelioma that grows slowly and responds well to treatment. It most commonly occurs in the abdomen of women, but can develop in the pleura as well.

    Learn more about epithelial mesothelioma
  • Sarcomatoid Mesothelioma

    Malignant sarcomatoid mesothelioma

    The least common of the three major histological subtypes, sarcomatoid mesothelioma is observed in about 10 to 20 percent of all cases. Because this subtype is particularly aggressive, survival is usually poor.

    Learn more about sarcomatoid mesothelioma
  • Biphasic Mesothelioma

    Malignant biphasic mesothelioma

    In about 20 to 35 percent of cases, mesothelioma tumors contain a mix of epithelial and sarcomatoid cells. This subtype is called biphasic mesothelioma. The ratio of epithelial to biphasic cells can vary significantly from case to case, which influences the patient’s outlook. When a biphasic tumor has a greater number of epithelial cells, survival is generally better.

    Learn more about biphasic mesothelioma

Clinical Trials

A growing number of patients are benefiting from clinical trials — experimental studies that test the effectiveness of new anti-cancer treatments and approaches to therapy. Researchers perform studies on nearly every type and subtype of mesothelioma, so it is likely you can find one for your specific diagnosis.

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Karen Selby is a registered nurse and a Patient Advocate at The Mesothelioma Center. She worked in several subspecialties within nursing before joining Asbestos.com in 2009.

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