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Mesothelioma tumors are categorized by their cell type: epithelioid, sarcomatoid, or biphasic. Each cell type responds differently to treatment and has an important effect on a patient’s prognosis.

One of the ways specialists classify mesothelioma is by the cell type of the tumor. Cell type is highly important because it plays a key role in determining the course of treatment and a patient’s prognosis. Specialists further divide these 3 types into various subtypes, each with its own unique characteristics.

The 3 Mesothelioma Cell Types

Epithelioid: Mesothelioma tumors made up of epithelioid cells are the most treatable. Patients with this cell type have the best prognosis. It’s the most common cell type. Learn More >

Sarcomatoid: The least common cell type, sarcomatoid mesothelioma has less treatment options than other cell types. Patients diagnosed with this cell type have the least favorable prognosis. Learn More >

Biphasic (mixed): Mesothelioma tumors made up of both epithelioid and sarcomatoid cells are called biphasic. Tumors with more epithelioid cells than sarcomatoid cells are more treatable and carry a better prognosis. Learn More >

Talk to an expert from our Patient Help Team to find the right doctor for your cell type.

How Doctors Determine Cell Type

The cell type of a mesothelioma tumor plays a key role in how a doctor develops a treatment plan. If a patient’s imaging tests show a tumor mass or fluid build up that may point to mesothelioma, the doctor takes a tissue or fluid sample of the area and sends it to the lab for testing. A pathologist then examines the sample under a microscope to confirm whether or not the patient has mesothelioma.

Special testing that confirms mesothelioma on a cellular level is called histology. This testing also reveals the cell type of the patient’s tumor.

Mesothelioma is difficult to distinguish from other cancers, like adenocarcinoma. This makes histological testing a critically important part of the diagnostic process.

Epithelioid Cell Type

The epithelioid cell type is the most common cellular form of mesothelioma and accounts for 50 to 70 percent of all diagnoses.

Epithelioid mesothelioma is easier to treat than other types because of the square shape of the epithelioid cells themselves. As they replicate and try to spread, their shape causes the cells to stick to each other. This slows their spread and makes curative treatment, like surgery or chemotherapy, more effective in removing the cancer from a patient’s body.

Specialists categorize epithelioid cells into subtypes for a more nuanced understanding on how the mesothelioma will affect a patient’s prognosis.

The most common and easiest to identify epithelioid cell subtypes include:

  • Tubulopapillary
  • Acinar
  • Adenomatoid
  • Solid mesothelial


Some epithelioid subtypes, like clear cell and deciduoid, are less common and can only be correctly identified by an experienced mesothelioma specialist.

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Sarcomatoid Cell Type

The sarcomatoid cell type is the least common cellular form of mesothelioma. It accounts for only about 10 percent of all mesothelioma diagnoses and is the most aggressive form of the disease.

Specialists consider it the most aggressive cell type because sarcomatoid cells spread quickly. This is due to their long, spindle-like shape and haphazard pattern of growth. As a result, surgery to remove a sarcomatoid tumor may not be effective if the cancer has spread.

Like epithelioid cells, sarcomatoid cells are catergorized into several subtypes, each responding differently to treatment.

Sarcomatoid subtypes include:

  • Desmoplastic
  • Lymphohistiocytoid
  • Transitional.


Biphasic (Mixed) Cell Type

Biphasic, or mixed, mesothelioma is the second most common cellular form of mesothelioma. It accounts for 20 to 35 percent of all mesothelioma diagnoses. On a microscopic level, a biphasic tumor is composed of epithelioid and sarcomatoid cells.

How well biphasic mesothelioma responds to treatment depends on the ratio of epithelioid and sarcomatoid cells. If the tumor is composed mostly of epithelioid cells, it will grow more slowly and respond better to treatment. If the tumor has more sarcomatoid cells, it will grow more quickly and be less responsive to treatment.

A biphasic mesothelioma tumor can be difficult to diagnose because epithelioid and sarcomatoid cells often grow in different parts of the same tumor.

If a doctor doesn’t have much experience with mesothelioma, it’s possible that he or she may misdiagnose a biphasic tumor as epithelioid or sarcomatoid. If you’ve been exposed to asbestos in the past, it’s best to consult a doctor with experience diagnosing mesothelioma.

Getting Treatment

Knowing the cell type of a mesothelioma tumor helps specialists create a treatment plan tailored to their patient’s diagnosis. For example, epithelioid cells respond better to aggressive surgery because they grow more slowly than sarcomatoid cells. An experienced specialist will consider cellular characteristics such as this when creating a course of treatment.

Cell type is, however, only one of a number of factors that determine how treatments will affect a patient’s prognosis. The location of the mesothelioma and its cancer stage are also very important factors specialists consider when they create a course of treatment for their patients.

If you’ve been diagnosed with mesothelioma, speaking to an experienced specialist who understands the disease on a cellular level is an important step towards improving your prognosis. Get help finding an experienced mesothelioma specialist now.