Mesothelioma Cell Types

Quick Summary

When a patient is diagnosed with mesothelioma, the specialist will also diagnose the mesothelioma cell type—a critical factor in determining prognosis and treatment. Whether you’ve been diagnosed with epithelioid, sarcomatoid or mixed cell type, there are treatment options that can improve your quality of life and possibly increase survival.

Mesothelioma Cell Type Overview

Mesothelioma is a complex cancer with different cell types that determine a patient’s diagnosis and the types of treatments that will be most effective.

If you’ve been diagnosed with mesothelioma, then here is what you need to know about cell types:

  • Mesothelioma has 3 cell types—epithelioid, sarcomatoid and biphasic (mixed)
  • Epithelioid is the most common cell type and has the best prognosis
  • Sarcomatoid is the least common cell type and has the worst prognosis
  • Biphasic mesothelioma tumors are those that contain both epithelioid and sarcomatoid cell types
  • Treatment options exist for all three cell types
  • Only an experienced mesothelioma pathologist has the skills required to determine the cell type, which often gets misdiagnosed
  • Cell type is just one factor in your mesothelioma diagnosis, along with location and stage

What Is a Mesothelioma Cell Type?

Mesothelioma cell types are the classifications of the individual mesothelioma cells found in a patient’s body. Essentially, they are the result of different types of genetic mutations that occur from asbestos exposure.

Cell type is a way of describing how mesothelioma cells look and behave when observed by a pathologist under a microscope.

Did you know

Cancer is a broad term to describe a condition whereby abnormal cells grow out of control. Where these cancer cells originate determines the type of cancer you have, such as mesothelioma, which first develops in the mesothelial lining of the chest, abdomen, heart or testicles. How these cells grow and divide determines their cell type, as each cell type has a unique set of defining characteristics.

Cell type is essential information in planning mesothelioma treatments. Certain cells grow and divide at high rates and in irregular ways, making it difficult to detect them all and remove them entirely.

Mesothelioma Cell Types

There are 3 broad mesothelioma cell types that researchers have identified. These cells at an individual level look and behave in certain ways when pathologists observe them using their microscopes. Collectively, these cell types make up a mesothelioma tumor, which continues to grow as more cells replicate themselves.

The 3 mesothelioma cell types are:

  • Epithelioid
  • Sarcomatoid
  • Biphasic—tumors mixed with both cell types

In rare cases, mesothelioma tumors can be deemed benign, meaning non-cancerous. This can happen when non-cancerous tumors form in the mesothelial linings of the chest, abdomen, heart or testicles. Doctors are still unsure of how benign mesothelioma tumors occur but continue to research rare cases like this as they arise.

Epithelioid Cells

In 50-70% of mesothelioma cases, doctors will find epithelioid cells in a mesothelioma biopsy—the process of collecting tumor samples and observing them under the microscope.

Epithelioid cells are genetic mutations of healthy epithelial cells—the cells responsible for building protective lining tissues such as those that line the surfaces of the chest (pleura), abdomen (peritoneum) or heart (pericardium).

Epithelioid is the most common mesothelioma cell type, the easiest to treat and has the best prognosis of all three cell types.

Some of the characteristics of epithelioid cells include:

  • Elongated shape
  • Behavior that causes them to lump together
  • Pink cytoplasm (the material that the cell is composed of)
  • Oval or elongated nucleus (the cell’s DNA center)

Learn more about the Epithelioid Cell Type.

Sarcomatoid Cells

In 10-15% of mesothelioma cases, doctors observe sarcomatoid cells in the patient’s biopsy samples. Sarcomatoid cells are genetic mutations of healthy cells found in connective tissues such as muscles, bones and cartilage.

Whenever cancer cells originate in connective tissues, they’re called sarcomas, which is how doctors named this condition sarcomatoid mesothelioma. Sarcomatoid cells come to be through a process known as epithelial-to-mesenchymal transition (EMT), which occurs when epithelial cells turn into mesenchymal cells—the cells found in the connective tissues.

Sarcomatoid is the least common mesothelioma cell type, the most difficult to treat and has the worst prognosis of all 3 cell types.

Some of the characteristics of sarcomatoid cells include:

  • Irregular, spindle-shaped cells
  • Can have more than one nucleus
  • Spread and seed quickly
  • Form nodule tumors instead of a lump or mass

Learn more about Sarcomatoid Cell Type.

Biphasic Tumors

In up to 30% of mesothelioma cases, doctors find both epithelioid and sarcomatoid cells in a patient’s biopsy sample. When a tumor contains both cell types, it’s known as a biphasic mesothelioma tumor, or “mixed cell type”.

The 2 cell types are usually isolated to different regions of a tumor. When doctors remove tumor samples during a biopsy, it’s important for them to take samples from multiple areas of the tumor to ensure they don’t miss a cell type.

Biphasic is the second most common mesothelioma cell type, and its prognosis and treatment options depend on the ratio between epithelioid and sarcomatoid cells.

Biphasic tumors take on the characteristics of whatever the dominant cell type is. If epithelioid cells make up the majority of the tumor, then it will grow in a localized mass. If sarcomatoid cells dominate, then the tumor will spread irregularly and to distant sites quicker.

For a tumor to be diagnosed as biphasic, it must contain at least 10% of either epithelioid or sarcomatoid cells to be classified as biphasic. If a tumor contains less than 10% of either cell type, then the tumor becomes classified as the other type.

Learn more about Biphasic Cell Type.

Mesothelioma Histology

It’s always helpful for mesothelioma patients to have a basic understanding of medical terminology and processes so they can take active roles in their treatment plans.

When scientists study cells under a microscope, it’s a field of biology called histology. When the cells being examined are thought to be cancerous, then they undergo histopathological testing, which means to study diseased cells.

Histopathologists examine biopsied tumor tissue and determine whether there are any mesothelioma cells present. They look for things like cell size, shape and behavior to help classify the mesothelioma cell type.

Misdiagnosing Cell Type

Histopathological examination is the only way to confirm a mesothelioma diagnosis. However, it can sometimes result in misidentification of cell types since some cells closely resemble other types of cells.

Various studies have shown that cell type misclassifications happen in 20% of cases during the initial biopsy.

In these cases, it’s only until after surgery that the actual cell-type is confirmed. Research into mesothelioma cell types is ongoing. Scientists continue to look for ways to improve cell type identification to prevent cell type misdiagnoses.

Treatment Options for Mesothelioma Cell Types

The 3 cell types of mesothelioma mean that tumors grow and spread differently depending on the type the patient has. Therefore, it’s incredibly important to have an experienced pathologist examine a patient’s biopsied tissue to confirm the cell type.

Mesothelioma cell type helps doctors determine how to best treat the tumors. Cell type can tell doctors whether the mesothelioma has a high chance of being resected (removed) or not.

If you’ve been diagnosed with mesothelioma, it’s critical to ask your team about your cell type and what specific treatment plan they have for your unique condition. As always, patients are highly encouraged to seek a second opinion on their diagnosis, including their cell type.

For more information on mesothelioma cell types, treatments and seeing a specialist, contact the Patient Advocates at Mesothelioma Help Now.

View Author and Sources

  1. Environmental Health and Preventive Medicine, “Pathology of mesothelioma.” Retrieved from: Accessed on December 29, 2017.
  2. Journal of Thoracic Oncology, “Accuracy of Diagnostic Biopsy for the Histological Subtype of Malignant Pleural Mesothelioma” Retrieved from: Accessed on December 29, 2017.

Last modified: January 25, 2019