Mesothelioma Types by Tumor Location

Types of mesothelioma cancer differ based on tumor location and tumor cell variant. Pleural mesothelioma is cancer in the pleural lining around the lungs. Mesothelioma most often develops on the outer surface of the lungs. Other sites include the abdomen, heart and testicles.

Peritoneal mesothelioma is cancer in the abdominal lining. This lining is the peritoneum and the second most common site of mesothelioma. Testicular mesothelioma affects the tunica vaginalis lining of the testes. The rarest variant is pericardial mesothelioma, cancer of the protective heart sac.

Each mesothelioma type can lead to different symptoms. Doctors treat mesothelioma by cell type, such as epithelioid or sarcomatoid, and stage. Rare cell subtypes include:

  • Well-differentiated papillary cells
  • Small cell
  • Deciduoid
  • Cystic
  • Desmoplastic
  • Adenomatoid
  • Heterologous

Mesothelioma prognosis depends on tumor location, cell type and response to treatment. Epithelioid cells are the most common type of cell found in mesothelioma tumors. They are the most responsive to treatment. 

Pleural Mesothelioma

Pleural Mesothelioma diagram
Diagram showing where pleural mesothelioma forms.

Pleural is the most common mesothelioma type. About 70% to 75% of cases occur in the pleura, the outer lung tissue. There are more clinical trial studies on pleural mesothelioma than any other variants.

Aggressive surgery provides the best outcome for early-stage pleural mesothelioma. Unfortunately, doctors often diagnose patients after symptoms appear in later stages.

Typical pleural mesothelioma symptoms include:

  • Shortness of breath
  • Chest pain
  • Weight loss
  • Fever
  • Fatigue

Most patients qualify for chemotherapy or radiation therapy. Many are also eligible for clinical trials or immunotherapy. These therapies can add months or years to life expectancy. Patients can live for three or more years after stage 1 treatment versus roughly 12 months at stage 4.

Peritoneal Mesothelioma

Peritoneal Mesothelioma, the type of mesothelioma affecting the abdomen
Diagram showing where peritoneal mesothelioma forms.

Peritoneal mesothelioma forms in the tissue that surrounds the abdominal organs. This variant accounts for 10% to 20% of all cases. The prognosis is better than the pleural type, although less research is available.

Symptoms of peritoneal mesothelioma include:

  • Abdominal pain
  • Abdominal swelling
  • Bloating
  • Loss of appetite
  • Bowel changes

About half of peritoneal mesothelioma patients are eligible for surgery with heated chemotherapy. This procedure, known as HIPEC, has let patients live five or more years after diagnosis.

Pericardial Mesothelioma

Pericardial Mesothelioma diagram
Diagram showing where pericardial mesothelioma forms.

The pericardial mesothelioma tumor type is very uncommon. Only about 200 cases exist in medical literature records. This accounts for approximately 1% of all mesothelioma cases. With surgery, some patients live beyond the average six-month life expectancy.

The pericardial form develops in the protective heart sac known as the pericardium. Symptoms of pericardial mesothelioma include:

  • Irregular heartbeat
  • Chest pain
  • Difficulty breathing
  • Cough

Life expectancies of the cases on record range between six weeks and 15 months.

Testicular Mesothelioma

Testicular Mesothelioma, the type of mesothelioma affecting the testes
Diagram showing where testicular mesothelioma forms.

Testicular mesothelioma develops in the outer lining of the testes called the tunica vaginalis. This form of mesothelioma is the rarest. Less than 100 cases are reported in the medical literature, making up less than 1% of all mesothelioma cases.

Symptoms include scrotal swelling and painless testicular lumps. Treatment options include surgery and chemotherapy, which can help people live more than two years after diagnosis, on average.

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Three Primary Mesothelioma Cell Types

The three mesothelioma cell types are epithelial, sarcomatoid and biphasic. Biphasic is a mix of the first two cell types. Mesothelioma doctors can tell the difference between cells based on how they look under a microscope. 

An additional form of the disease includes benign mesothelioma, which is neither asbestos-related nor cancerous. Asbestos exposure causes cancer known as malignant mesothelioma.

Different mesothelioma tumors respond differently to various treatments. Epithelial or epithelioid cells respond the best, and sarcomatoid cells are more resistant to treatment. The biphasic subtype includes a mixture of both epithelial and sarcomatoid cells. 

Cancer doctors take these differences into account when planning your mesothelioma treatment. The incidence of these cell types varies by cancer location.

Prevalence of Mesothelioma Tumors and Cell Types

Cell Type Pleural Tumors Peritoneal Tumors
Epithelioid 50% 75%
Sarcomatoid 20% 4%
Biphasic 30% 24%
Source: Journal of Surgical Research, 2015

Based on the limited number of cases reported in the medical literature, pericardial mesothelioma exhibits a roughly equal distribution of the three mesothelioma cell types.

Approximately two-thirds of testicular mesothelioma cases contain exclusively epithelial cells. The remaining third testicular cases are biphasic. Only one case of purely sarcomatoid cell disease is on record for testicular mesothelioma.

Epithelial mesothelioma cells under a microscope.
A pathology stain showing epithelial mesothelioma cells under a microscope.

Epithelial Cell Subtype

Epithelioid mesothelioma makes up approximately 70% to 75% of all cases of asbestos-related mesothelioma cancers.

Patients with epithelioid cell tumors have the best prognosis. This subtype tends to be less aggressive and doesn’t spread as quickly as sarcomatoid and biphasic cell disease.

About 50% of pleural disease is epithelioid. Around 75% of peritoneal tumors are epithelioid.

Sarcomatoid Cell Subtype

Sarcomatoid mesothelioma is the least common mesothelioma cell category. It is the most aggressive and challenging to treat. It accounts for around 10% to 20% of all mesothelioma diagnoses.

You may hear sarcomatoid mesothelioma referred to as sarcomatous, spindle or diffuse malignant fibrous mesothelioma.

About 20% of pleural tumors are sarcomatoid, while only 1% of peritoneal mesothelioma are sarcomatous.

Biphasic mesothelioma cells under a microscope.
A pathology stain showing biphasic mesothelioma cells under a microscope.

Biphasic Cell Subtype

Biphasic mesothelioma refers to tumors that contain epithelial and sarcomatoid cells. Life expectancy after diagnosis with biphasic mesothelioma depends upon which cancer cell appears most frequently in the patient.

More epithelioid cells generally mean a better prognosis. If the tumor is primarily sarcomatous, it is harder to treat, and life expectancy is shorter.

Around 30% of pleural and 25% of peritoneal tumors are biphasic.

“Sarcomatoid, mixed (biphasic) and epithelial express themselves within the patient in a different manner. It’s important to understand which of these three types the physician is dealing with in a patient.”
Dr. Sugarbaker
Watch: Dr. David Sugarbaker explains the three mesothelioma cell types: Epithelial, Sarcomatoid and Biphasic.

Rare Mesothelioma Cell Subtypes

Rare cell types of mesothelioma are typically further subtypes of sarcomatoid, epithelioid and biphasic types. These are more irregular forms of mesothelioma that doctors may find difficult to diagnose. These variations have slightly different characteristics that affect the mesothelioma patient’s prognosis and life expectancy.

For example, patients with sarcomatoid tumors tend to have lower life expectancies than patients with epithelial tumors. However, some patients with the lymphohistiocytoid subtype of sarcomatoid cells have survived as long as six years.

  • Well-differentiated papillary cells commonly occur in peritoneal mesothelioma. Only a handful of cases exist of people with other mesothelioma cancer locations.
  • Small cell mesothelioma is another cell type that occurs more commonly in the abdomen.
  • A little more than half of the cases of deciduoid mesothelioma occur in the abdomen. Slightly less than half arise in the lung lining.
  • Cystic and papillary cells are more common in peritoneal mesothelioma.
  • Desmoplastic and lymphohistiocytoid are more common in pleural mesothelioma.
  • Adenomatoid cells can occur in both malignant mesothelioma and benign mesothelioma.
  • Heterologous cells are present in tumors that may also contain bone, cartilage and soft tissue.

Researchers have noted conflicting survival data for the heterologous subtype. Researchers also stressed the importance of determining the true incidence of this subtype, which is presently unknown.

For patients with rare cellular subtypes, treatment is similar to the overarching cell type. For example, patients with lymphohistiocytoid tumor cells are likely to respond well to immunotherapy, a treatment effective against sarcomatoid cells.

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Treatment by Type of Mesothelioma

Your specific mesothelioma diagnosis will influence your treatment options. Different treatments may be available depending on the location of your cancer and possibly the cell type.

To find the proper mesothelioma treatment for each patient, doctors consider many factors, such as cancer stage, cell type, patient’s age and overall health. The patient’s provider will also evaluate the patient’s desires and needs going into treatment.

Surgery is an appropriate option for early-stage patients who are younger and in good health. Chemotherapy, radiation therapy and immunotherapy are available to a broader range of patients, and a mesothelioma treatment plan is often multimodal, involving multiple therapies.  

Surgery

The recommended surgeries for pleural mesothelioma are extrapleural pneumonectomy or pleurectomy and decortication. Extrapleural pneumonectomy involves the removal of the cancerous lung and associated structures. Pleurectomy removes the entire pleura, and decortication consists of removing visible tumors from the chest cavity. 

Surgeons remove peritoneal tumors with a peritonectomy, which involves removing the peritoneal tissue in the abdomen. The surgery for pericardial tumors is a pericardiectomy, which removes the protective sac surrounding the heart. For testicular mesothelioma, surgeons perform an inguinal orchiectomy.

Chemotherapy Drugs

A combination of cisplatin and Alimta (pemetrexed) is the most effective regimen against pleural mesothelioma. Combinations of gemcitabine, Alimta, mitomycin and carboplatin are most effective against peritoneal mesothelioma.

No particular chemotherapy regimen is consistently effective for pericardial or testicular mesothelioma. The two latter types of mesothelioma are so uncommon and do not have a standardized treatment recommendation.

A mesothelioma expert oncologist can devise the best treatment plan based on their experience and your overall health in these rare situations.

Radiation Therapy

In pleural mesothelioma, specialists use radiation therapy with and without surgery. Radiation therapy isn’t a typical treatment for peritoneal mesothelioma due to its tendency to damage vital organs throughout the abdomen.

However, some doctors have successfully used radiation therapy to treat pericardial and testicular mesothelioma.

Palliative Treatment

The goal of palliative therapy is to alleviate pain and other symptoms of mesothelioma. Palliative care can significantly improve the quality of life and well-being of mesothelioma patients.

For example, palliative procedures include thoracentesis to drain fluid around the lungs and paracentesis to remove fluid from the abdomen. These procedures can alleviate pain and pressure and make breathing and eating easier for you.

Common Questions About Types of Mesothelioma

What is the difference between mesothelioma cell types and tumor location?

Tumor location refers to where the cancer first began growing such as the lining of the lungs or abdomen. Cell type refers to the type of cells that make up the tumors.

How does the type of mesothelioma impact prognosis and treatment?

The type of mesothelioma a patient has impacts which treatments will be recommended and their overall prognosis. Mesothelioma treatment is complex, and many other factors influence treatment options and prognosis such as the stage of the cancer.

How can I find a mesothelioma specialist for my type of mesothelioma?

You can speak with a Patient Advocate to find a mesothelioma specialist who has experience treating your type of mesothelioma.

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