Mesothelioma cell types include epithelioid, sarcomatoid, and biphasic (mixed). Cancer doctors can identify each cell type by examining tissue samples under a microscope. Each cell type affects a patient’s prognosis and treatment options differently. Learn about each mesothelioma cell type below.
What Are the Different Mesothelioma Cell Types?
A patient with mesothelioma can have one of three mesothelioma cell types. Which cell type a patient has depends on the cells that make up their cancer tumors.
The three mesothelioma cell types are:
- Epithelioid mesothelioma: This is the most common cell type. Epithelioid cells are shaped like rectangles. Roughly 7 or 8 out of 10 mesothelioma patients will have this cell type. It is also known as epithelial mesothelioma.
- Sarcomatoid mesothelioma: About 1 or 2 out of 10 mesothelioma patients have sarcomatoid mesothelioma. Sarcomatoid mesothelioma cells are spindle-shaped and spread very quickly.
- Biphasic mesothelioma: Patients have this type if their tumors are made up of both sarcomatoid and epithelioid cells. Around 2 to 3 in 10 mesothelioma cases are biphasic. This type is also known as mixed mesothelioma.
Mesothelioma cell types have a big impact on life expectancy and treatment plans, as some are easier to treat than others. Epithelioid cells are the easiest to treat, while sarcomatoid cells are more aggressive and harder to treat.
Thankfully, a variety of treatment options are available no matter what mesothelioma cell type a patient has. U.S. veterans with mesothelioma can get medical care from military and civilian hospitals across the country. Learn more with a Free Veterans Packet.
Top Facts About Mesothelioma Cell Types
- All types of mesothelioma cancer cells can be misdiagnosed. Doctors may ask a patient about their asbestos exposure history to rule out other illnesses.
- There are many subtypes of mesothelioma cells. Learn about seven of these subtypes below.
- Early diagnosis and aggressive treatments are essential to living longer with any mesothelioma cell type.
Diagnosing Mesothelioma Cell Types
Generally speaking, the steps to diagnosing all mesothelioma cell types are the same. If a doctor thinks their patient has mesothelioma, they’ll confirm the diagnosis by taking a biopsy. During a biopsy, a sample of possibly cancerous fluid or tissue is extracted and sent to a pathology lab for examination.
In the lab, pathologists carefully examine the fluid or tissue sample they’ve received under a microscope. Pathologists will then compare the samples to existing cell profiles to identify the cell type a patient has.
Mesothelioma cells can often resemble other types of cancer and noncancerous cells, so doctors may also need to use a technique called immunohistochemistry when making a diagnosis. This test screens the tumors for proteins or other substances in the cells that are unique to mesothelioma tumors.
Pathologists can then notify the patient’s doctor after a mesothelioma diagnosis is confirmed.
Epithelioid mesothelioma is the most common cell type of mesothelioma. It makes up about 70% to 80% of all cases.
Epithelioid mesothelioma occurs when healthy epithelial cells mutate. Epithelial cells line the tissues of organs, glands, and skin, and exist in almost every part of the body.
Epithelioid mesothelioma cells have the following characteristics:
- Clumped formation
- Cube or rectangle shape
- Defined nuclei (cell center)
- Slower growth than other cell types
According to the UPMC Hillman Cancer Center, epithelioid mesothelioma cells divide quickly but stick together. As a result, epithelioid mesothelioma metastasis (spread) doesn’t happen as quickly as with the other cell types.
Epithelioid Mesothelioma Life Expectancy and Survival Rates
Epithelioid mesothelioma patients have the best prognosis of all mesothelioma cell types since this type spreads slowly.
A patient’s prognosis is measured by life expectancy (the average time a patient lives after diagnosis) and survival rate (number of patients still alive after a period of time).
- The average life expectancy for epithelioid mesothelioma patients is 18 months.
- The 2-year survival rate for epithelioid mesothelioma is 65% in patients treated with surgery, chemotherapy, and radiation. The 5-year survival rate for these epithelioid mesothelioma patients is 27%, according to the Dana-Farber Cancer Institute.
Some epithelioid patients may live even longer depending on the treatments they qualify for and when they’re diagnosed.
Epithelioid Mesothelioma Subtypes
There are several subtypes of each mesothelioma cell type. Learn about the different epithelioid mesothelioma subtypes below.
Adenomatoid mesothelioma is also known as glandular mesothelioma. It’s rather rare, making up 6% of pleural mesothelioma cases (the most common type of this cancer, affecting the lung lining). Under a microscope, adenomatoid mesothelioma cells look like cubes or rings.
This mesothelioma cell type can be mistaken for a benign (noncancerous) tumor in some cases. As a result, doctors need to be extra careful if they think a patient has adenomatoid mesothelioma in order to avoid a misdiagnosis.
Cystic mesothelioma is a subtype that’s often found in cases of peritoneal mesothelioma (which forms in the abdominal lining). Cases of cystic mesothelioma are benign (noncancerous) — however, patients can still die from these tumors without treatment.
Doctors must also be sure to completely remove all of the cancer tumors via surgery if possible, as this mesothelioma cell type is prone to growing back (recurring).
Deciduoid mesothelioma is extremely rare. As of 2020, there had only been around 50 reported cases in pleural mesothelioma patients. For context, roughly 2,400 cases of pleural mesothelioma are diagnosed every year.
Deciduoid mesothelioma is often seen in younger women diagnosed with peritoneal mesothelioma, but it can affect anyone. Further, some cases were seen in people with no known history of asbestos exposure.
Lymphohistiocytoid mesothelioma is another rare subtype, making up less than 1% of all mesothelioma diagnoses. These cells resemble other forms of cancer under a microscope (like non-Hodgkin’s lymphoma).
Doctors once thought this mesothelioma cell type was a subtype of sarcomatoid mesothelioma. However, medical experts later learned that patients with lymphohistiocytoid mesothelioma could live for up to 18 months in some cases. This cell type is now considered an epithelial mesothelioma subtype as a result.
Small Cell Mesothelioma
Small cell mesothelioma appears similar to small cell lung cancer tumors under a microscope.
Because it’s so similar to small cell lung cancer, pathologists need to be especially careful when diagnosing a possible case of small cell mesothelioma. Lung cancer is much more common than mesothelioma and requires different medical treatments.
However, doctors can tell the difference between small cell lung cancer and mesothelioma using immunohistochemistry.
Well-Differentiated Papillary Mesothelioma
This mesothelioma cell type is often found in cases of peritoneal mesothelioma or testicular mesothelioma (which affects the tunica vaginalis, the testicle lining). It’s also more common among female patients than male patients.
Sarcomatoid mesothelioma cells are spindle-shaped and look like the cells of bone and soft-tissue cancers called sarcomas. Sarcomatoid cells are the least common type of mesothelioma cancer cell, only found in 10% to 20% of cases.
Sarcomatoid mesothelioma is also known as spindled mesothelioma due to its distinct cell shape.
Sarcomatoid cells have the following characteristics:
- Fast growth compared to other cell types
- Large nuclei
- Long, large, and spindle-shaped
According to the Moffitt Cancer Center, the spindle shape makes it hard for sarcomatoid cells to stick together. This means they’re more likely to break away from the main tumor and spread to other parts of the body. As a result, sarcomatoid mesothelioma spreads faster and is harder to treat than the other cell types.
Sarcomatoid Mesothelioma Survival Rates and Life Expectancy
Sarcomatoid mesothelioma has a poor survival rate since it spreads quickly and is very aggressive.
- The average life expectancy for sarcomatoid mesothelioma is about 7 months.
- The 2-year survival rate for sarcomatoid mesothelioma patients was 20% in a study from the Dana-Farber Cancer Institute. There were no reported sarcomatoid mesothelioma survivors at the study’s 5-year mark, but some patients can become long-term survivors with proper medical care.
Aggressive treatment is often highly recommended to patients diagnosed with this mesothelioma cell type. Treatments are the only way to help sarcomatoid mesothelioma patients live longer.
Sarcomatoid Mesothelioma Subtypes
Like epithelioid mesothelioma, sarcomatoid mesothelioma also has its own subtypes. Learn about common ones below.
Desmoplastic mesothelioma is found in roughly 10% of all mesothelioma cases. The tumors of this type of mesothelioma cell are made up of dense, fiber-like tissue that’s not cancerous, as well as actual cancer cells.
Because of this, desmoplastic mesothelioma may be mistaken for noncancerous conditions like an inflamed lung lining (pleurisy), depending on where it develops in the body.
Transitional mesothelioma is unique, as scientists are still debating which mesothelioma cell type it should belong to. Transitional mesothelioma cells aren’t clearly shaped like the spindles of typical sarcomatoid cells, but they’re also missing the defining features of epithelioid cells.
That said, the medical journal Translational Lung Cancer Research found that transitional mesothelioma cells are genetically more similar to sarcomatoid cells, and that transitional patients have survival times similar to general sarcomatoid patients.
Biphasic mesothelioma accounts for 20% to 30% of mesothelioma cases, according to the American Cancer Society (ACS).
Biphasic mesothelioma occurs when a patient has both epithelioid and sarcomatoid cells in the same tumor. There may be more epithelioid or more sarcomatoid cells present.
“BMM [biphasic malignant mesothelioma] is characterized by having at least 10% of each epithelioid and sarcomatoid component.”
— Translational Lung Cancer Research
Biphasic Mesothelioma Life Expectancy and Survival Rates
Patients with biphasic mesothelioma often have a better prognosis than those with sarcomatoid mesothelioma but a worse one than epithelioid patients.
- Biphasic mesothelioma has an average life expectancy of around 10 months.
- The typical 5-year survival rate for biphasic mesothelioma is 20%.
However, survival times greatly depend on the ratio of epithelioid and sarcomatoid cells present in the patient’s tumor.
Cases of biphasic mesothelioma where there are more epithelial cells present may be easier to treat than if there are more sarcomatoid cells. Thus, these biphasic mesothelioma patients may live longer.
Treating Your Mesothelioma Cell Type
Mesothelioma treatments are key to improving the survival time and quality of life for patients with any mesothelioma cell type.
The most common treatments for mesothelioma are surgery, chemotherapy, immunotherapy, and radiation. Doctors often combine one or more treatments to give patients the best chance possible at fighting their disease.
Surgery and Mesothelioma Cell Types
Mesothelioma surgery allows doctors to remove all visible cancer tumors from the body. Surgery is often the best way to improve mesothelioma life expectancy, but it’s not ideal for all cases.
Mesothelioma surgery is often recommended for epithelioid mesothelioma patients since this cell type doesn’t spread as quickly.
“The epithelial subtype, which is the most common, is the one that is the most amenable to surgical intervention.”
— Dr. Joseph Friedberg, Mesothelioma Specialist, University of Maryland Medical Center
Patients can live very long with surgery in some cases. A 2017 study looked at 19 patients with advanced epithelioid cells that hadn’t spread to nearby lymph nodes.
Each patient had stage 3 or 4 malignant pleural mesotheliomas, which have median life expectancies of 16 and 12 months, respectively. However, the patients lived for over 7 years on average thanks to a lung-sparing surgery called pleurectomy with decortication (P/D).
Other studies are currently looking at how patients with early-stage biphasic and sarcomatoid mesothelioma can benefit from surgery. For example, a P/D showed a 40% increase in survival among sarcomatoid mesothelioma patients in a 2018 study.
Learn about surgery and other mesothelioma treatments in our Free Veterans Packet.
Mesothelioma Cell Types and Other Treatments
Besides surgery, doctors can treat different types of mesothelioma cells using other treatments.
Other treatments include:
- Chemotherapy: Cancer-killing drugs used to destroy mesothelioma cells and shrink tumors
- Immunotherapy: Medications that boost the body’s immune system so it can fight cancer
- Radiation therapy: High-powered but painless energy beams that doctors use to shrink tumors
Epithelioid cells tend to have more treatment options than sarcomatoid cells, but treatments — including surgery — may still be an option for all patients. However, life-extending treatments aren’t usually possible if the cancer has spread throughout the body.
Patients with any cell type should work with mesothelioma specialists to discuss their treatment options.
Getting Treatment & Help for Any Mesothelioma Cell Type
No matter your mesothelioma cell type, the best way to live longer is to seek treatment from a specialist. Mesothelioma specialists can tailor treatment plans to your mesothelioma cell type.
Mesothelioma specialists work at cancer centers across the country. Further, the U.S. Department of Veterans Affairs (VA) works with several top mesothelioma specialists to get veterans the best care possible.
Additionally, we have a team of in-house Patient Advocates who can help veterans with mesothelioma find treatment, file for VA benefits, and pursue financial compensation.
FAQs About Types of Mesothelioma Cancer Cells
Why are biopsies important in diagnosing mesothelioma cell types?
Biopsies are the only way to diagnose a person with mesothelioma and determine their cell type. Biopsies allow doctors to extract a sample of potentially cancerous tissue or fluid for examination.
A common biopsy procedure is a thoracoscopy, which is a way to see the lung tissue using a camera and a flexible tube. A surgical or needle biopsy may be performed instead when a direct path to the affected area is available.
After a biopsy has been extracted, doctors will examine the sample under a microscope and see which mesothelioma cells (if any) are present.
What is mesothelioma histology?
Histology is the study of cells and other organisms under a microscope. Histology is crucial to diagnosing a patient’s mesothelioma cell type.
Pathologists must carefully examine all biopsy samples they receive to confirm whether the patient has mesothelioma. If so, pathologists must also determine what type of mesothelioma cells are present.
What is the most common mesothelioma cell type?
The most common mesothelioma cell type is epithelioid mesothelioma. It accounts for about 70% to 80% of all mesothelioma cases. Thankfully, it is also the easiest type of mesothelioma cell to treat.
Is it difficult to diagnose mesothelioma cell types?
It can sometimes be difficult to accurately diagnose a mesothelioma patient’s cell type since the cancer is very rare and may look like a wide range of other conditions under a microscope.
Further, biopsy samples only observe a small piece of a tumor. Pathologists might only see one type of cell when the other could also be present on a different part of the tumor. Doctors may need to collect large tumor samples to identify biphasic mesothelioma as a result.
If you or your loved one believes they were diagnosed with the wrong mesothelioma cell type — or the wrong condition entirely — reach out to a doctor for a second opinion. A second opinion can confirm the original diagnosis or provide a new one.