Mesothelioma Cells

What Are the Different Types of Mesothelioma Cells?

Mesothelioma tumors contain epithelioid, sarcomatoid or biphasic cells. Epithelioid cells are the most common. Each cell type influences how the tumor grows and responds to treatment. Doctors study these cells through histology to identify their characteristics and customize a treatment plan for you.

Key Facts About Mesothelioma Cells

1. A biopsy is the only way to confirm mesothelioma cell type. Pathologists then study the tissue through histology to identify cell characteristics.
2. Cell type and tumor location determine which treatments are available, including surgery eligibility, chemotherapy protocols and whether immunotherapy is appropriate.
3. A peritoneal mesothelioma study found a median survival of 55 months for people with epithelioid cells. People with sarcomatoid or biphasic cells had a median survival of 7 to 13 months.
4. Epithelioid cell types often respond well to chemotherapy. Sarcomatoid and biphasic types are increasingly treated with immunotherapy such as Opdivo (nivolumab) and Yervoy (ipilimumab).

Studying mesothelioma cells and tissues under a microscope is called histology. It helps reveal their structure and behavior. Histology captures key details about mesothelioma cells, which doctors note in your pathology report.

Epithelioid cells often form clusters or sheets of oval or cube-shaped cells with clear centers visible under a microscope. Sarcomatoid cells are rarer and spindle-shaped. Biphasic cells are a mix of epithelioid and sarcomatoid. A few rare subtypes exist, but most cases fall into these 3 categories.

Epithelial Mesothelioma Cells

Epithelioid mesothelioma cells respond better to treatment than other types, offering the most favorable prognosis. They’re typically uniform with somewhat predictable growth patterns. These tumors aren’t as aggressive and respond well to intensive treatment like surgery and chemo.

Pleural mesothelioma survivor Christine Shippen shared her advice with us. She said, “Be advised by your doctor or oncologist what the best treatment is for you. There are other treatments available depending on how fit you are.”

Reflecting on her 6 years as a survivor, she added, “Give yourself time to come to terms if you can. The longer I live, I continue to thank God for giving me the willpower to believe I will fight the fight to the end. My perspective remains always positive.”

Sarcomatoid Mesothelioma Cells

Sarcomatoid mesothelioma cells occur in 10% to 20% of cases. They’re associated with the least favorable prognosis and the most limited response to standard treatments. This is the most aggressive cell type, which can make treatment more challenging. Sarcomatoid cells develop quickly and don’t respond as well to typical treatments. People with this cell type often receive a diagnosis at later mesothelioma stages and may need more aggressive treatment protocols.

Diagnosed with sarcomatoid mesothelioma, Wally Rogers far surpassed his initial prognosis. After experiencing serious side effects from chemo, Wally tried Keytruda (pembrolizumab), saying, “It’s a real mystery at this point why I’ve done so well. After listening to the medical people, it’s almost shocking. I’m not superhuman by any means. I’m a simple man. Maybe I can let people know, there is hope out there.”

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Biphasic Mesothelioma Cells

Biphasic mesothelioma cells are a combination of epithelioid and sarcomatoid cells. This mixed cell type accounts for 20% to 30% of mesothelioma cases. To receive a biphasic diagnosis, each cell type must account for at least 10% of the tumor mass.

Since biphasic tumors contain mixed cell types, they can be challenging to diagnose accurately from smaller biopsies. Prognosis for biphasic mesothelioma depends on the dominant cell type. People with a higher proportion of epithelioid cells generally have better outcomes.

Expert Insight

“Cisplatin and carboplatin combination is usually the gold standard” for people with epithelioid mesothelioma cells. For people with sarcomatoid and biphasic mesothelioma cells, “immunotherapy is often the go to now.”

Karen Selby , Registered Nurse and Patient Advocate

Rare Mesothelioma Cell Types

Some mesothelioma tumors contain rare subtypes that don’t fall into one of the main categories. These unusual cell types can make diagnosis more complex and may influence how the cancer responds to treatment.

Rare Forms of Mesothelioma Cell Types

• Adenomatoid: A subtype of epithelioid cells, these cells resemble gland-like structures and often appear in the peritoneum.
• Benign: Benign mesothelioma isn’t cancerous and doesn’t result from asbestos exposure.
• Cystic: A subtype of epithelioid, cystic mesothelioma features smooth, thin-walled cysts held together with fragile fibrovascular tissue.
• Deciduoid: Extremely rare and most often found in young women with peritoneal mesothelioma.
• Desmoplastic: Composed of dense, fibrous tissue, desmoplastic mesothelioma is usually grouped within the sarcomatoid category.
• Heterologous: Tumors of heterologous cell types contain bodily tissues different from those in which they form. Only a handful of cases exist in medical literature.
• Lymphohistiocytoid: A subtype of sarcomatoid, lymphohistiocytoid mesothelioma mimics inflammatory or immune system tissue and may be confused with benign conditions.
• Small cell: Small-cell mesothelioma occurs when a large proportion of a tumor contains small cells that grow in a pattern similar to small-cell carcinoma.
• Well-differentiated papillary: A variant of epithelioid mesothelioma, papillary mesothelioma cells usually grow slowly and can resemble healthy cells.

These rare cell types often require advanced pathology testing. Doctors base treatment decisions on the cells’ dominant behavior and whether they act more like epithelioid or sarcomatoid mesothelioma. Specialized staining techniques and histology, where doctors examine tissue samples under a microscope, are especially important for accurately identifying these rare variants.

How Do Doctors Identify Mesothelioma Cell Types?

To find out your specific mesothelioma cell type, pathologists take a small piece of tissue from a biopsy. They look at it under a microscope using chemical stains that make the cells’ features stand out. They study the cells to see what they look like and how they function.

Special tests, like immunohistochemistry, help doctors find specific markers on the cells. Knowing the cell type helps cancer doctors diagnose mesothelioma and choose the best treatment plan based on how the cancer might behave.

Other Ways Pathologists Learn About Mesothelioma Cells

Pathologists use special tests and advanced tools to study mesothelioma cells. These methods show detailed features of the cells’ structure, genes and proteins. They also reveal how the cells grow, change shape and interact with their surroundings. This helps doctors understand how aggressive the cancer might be, how it behaves and how it may respond to different strategies.

Tools for Studying Mesothelioma Cells

• Cell staining: Checks for specific proteins in mesothelioma cells using special stains to help with diagnosis and treatment choices.
• Electron microscope: This microscope shows a very clear and detailed picture of the cells to help tell mesothelioma apart from other cancers.
• Gene analysis: This test, called a cytogenetic test, checks if the cancer cells have changes in their chromosomes to help with diagnosis.
• Molecular testing: Finds gene changes that might respond to treatments like targeted therapy, which blocks genes that help mesothelioma cells grow and spread.
• Protein profiling: A test called flow cytometry checks proteins on cancer cells’ surfaces to see how the cells respond to treatments.

All of these assessments help to create a more complete understanding of mesothelioma cells. Your doctors use this information to understand how each individual mesothelioma case operates on a cellular level and develop a treatment plan that works best for you.

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How Cell Type Affects Mesothelioma Prognosis and Treatment

Mesothelioma cell types affect outcomes because they change how cancer cells and their surroundings behave. Slower-growing types like epithelioid respond better to surgery and medicines because their tumors let treatments and the immune system work more easily. Faster-growing types like sarcomatoid build thick tissue that blocks treatment and immune system defenses, making them harder to treat. These differences also affect how well newer treatments like immunotherapy work.

When doctors look at biopsy results, they can decide if surgery is a good option or if relieving symptoms with palliative care is better. These results also help doctors and patients have clearer conversations about what’s ahead, allowing them to prepare with their families for their mesothelioma journey.

New treatments are helping some people with mesothelioma live longer. In a 2025 study in the International Journal of Clinical Oncology, immune checkpoint inhibitors Opdivo and Yervoy improved progression-free survival for almost 11 months in some people. Overall survival was significantly better in patients with the epithelial cell type. 

Common Questions About Mesothelioma Cells

Which mesothelioma cell type has the best prognosis?

Epithelioid mesothelioma has the most favorable prognosis of the 3 cell types. A peritoneal mesothelioma study found a median survival of 55 months for people with epithelioid cells. Outcomes vary depending on tumor location and treatment, so it’s important to talk with your doctor about what to expect.

What is mesothelioma histology?

Histology is the microscopic study of tissue. Doctors use mesothelioma histology to identify cell type and make informed treatment decisions based on how the cells look and behave.

How does sarcomatoid mesothelioma differ from epithelioid?

Epithelioid cells are the most common, making up 50% to 70% of cases, and they respond better to treatment. Sarcomatoid cells occur in 10% to 20% of cases and carry the least favorable prognosis with the most limited response to standard treatments. Doctors increasingly treat sarcomatoid mesothelioma with immunotherapy rather than surgery or chemotherapy.

Can immunotherapy treat all mesothelioma cell types?

Immunotherapy isn’t the first choice for every cell type. It’s been found to be most effective for people with sarcomatoid and biphasic mesothelioma. A 2025 study in the International Journal of Clinical Oncology found that Opdivo and Yervoy improved progression-free survival for almost 11 months in some people.

What do mesothelial cells indicate?

Healthy mesothelial cells line the lungs, the abdomen and the heart sac. Pathologists study healthy and abnormal mesothelial cells through histology to understand how asbestos exposure causes cellular changes. Asbestos irritates the lining and triggers tumor growth, turning healthy cells malignant.

Can mesothelioma have more than one cell type?

Yes. Biphasic mesothelioma has both epithelial and sarcomatoid cells within one tumor. The dominant type will determine the characteristics of the cancer and the treatment.

Do mesothelioma cell types change over time?

Generally, no. People with mesothelioma usually don’t have a different type over the course of their treatment or disease. Treatment response and the way tumors develop may vary throughout the progression of mesothelioma.

Is cell type more important than stage in mesothelioma prognosis?

Both mesothelioma cell type and how far the cancer has spread are important. Cell type informs aggressiveness and response to treatment, while stage indicates the ability to spread. They factor into prognosis upon first diagnosis and affect the care you’ll receive.

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