Mesothelioma Cell Types
Cell Types of Mesothelioma

Epithelioid

Sarcomatoid

Biphasic
The pathologist also uses various types of tests to look for the presence of particular proteins in the sample. Depending on the appearance of the cells under the microscope, the pathologist will select which tests would be the most useful. These tests help ensure an accurate diagnosis since many different types of cancer cells can closely resemble each other in a tissue sample.
It’s important to determine the cell type accurately because it has a significant impact on the prognosis and treatment options for a particular patient.
- Medically Reviewed By: Patricia Shelton, M.D.
- Legally Reviewed By Kevin LaMarca
- Last Modified July 26, 2022
Epithelioid Mesothelioma
Regularity of the cells
n epithelioid mesothelioma, all of the cells are approximately the same size and shape.
Square-shaped or columnar cells
which have a single nucleus in each cell. The nucleus is the part of the cell that houses the DNA and can be seen under a microscope as a spot inside of the cell.
Discrete sheets or clumps of cells
The cells of this cell type tend to stick together, causing them to form sheets or clumps. This means that the cancer doesn’t spread as easily around the body, and it’s also easier to remove surgically.
Rapid cell division
The cells of epithelioid mesothelioma tend to divide rapidly, which means that the tumor grows quickly.
Epithelioid mesothelioma can closely resemble other types of cancer, including some common types of lung cancer and breast cancer. In some cases, epithelioid mesothelioma may be misdiagnosed as one of these cancers. Getting a second opinion on your diagnosis may be beneficial to ensure the right treatment plan can be created.
Sarcomatoid Mesothelioma
Irregular cell shapes
arcomatoid cells tend to vary in shape and size and are more irregular than epithelioid cells.
Spindle-shaped cells.
The cells of this type are generally long and thin and tapered at both ends.
Small nodules or bundles of cells.
Rather than forming larger sheets or clumps, sarcomatoid cells tend to be found in smaller groups. Unlike in epithelioid tumors, they generally don’t form glandular structures.
Slower cell growth
Sarcomatoid cells tend to divide less often than epithelioid cells do, so the tumor will generally grow at a slower rate.
Cells that separate easily
Sarcomatoid cells are less likely to stick together than epithelioid cells. They can more easily separate from each other, which allows them to spread more easily, both within the tissues of the area and more widely around the body. This characteristic accounts for the poorer prognosis associated with this cell type.
There are a few subtypes of sarcomatoid mesothelioma, including desmoplastic and lymphohistiocytoid. These share the overall features of sarcomatoid mesothelioma but differ in some specifics of cell and tissue structure.
Sarcomatoid mesothelioma can also closely resemble other types of cancer, including sarcomas, which are tumors that arise from connective tissue. Misdiagnosis can occur, and it may be beneficial for patients to seek a second opinion on their diagnosis before committing to a treatment plan.
Biphasic Mesothelioma
The characteristics of biphasic mesothelioma include:
A mixture of epithelioid and sarcomatoid cells,
which are present in the same tumor. The pathologist will see cells of both types when looking at the sample under the microscope.
At least 10 percent
of the tumor must be made up of each cell type in order for it to be diagnosed as biphasic. For example, if 95 percent of the cells in a tumor are epithelioid and only five percent are sarcomatoid cells, then it will be diagnosed as epithelioid, not biphasic. In this case, there are not enough sarcomatoid cells for them to be considered significant. However, if the tumor is 85 percent epithelioid and 15 percent sarcomatoid, then it will be diagnosed as biphasic.
Prognosis by Cell Type
Treatment can make a difference in life expectancy for mesothelioma patients, although the effectiveness of particular treatment options is also impacted by cell type. Patients with epithelioid mesothelioma tend to receive more benefit from certain treatment options than those with sarcomatoid tumors.

Treatment Options by Cell Type
Surgery
Patients with epithelioid tumors are often good candidates for surgery as long as their cancer has been found in a relatively early stage. This is because epithelioid cells tend to stick together more closely, making them easier to remove through surgery. However, patients with sarcomatoid tumors are not as likely to respond well to surgery. Because sarcomatoid cells tend to spread apart from each other, some cancer cells are likely to be left behind after surgery.
A 2018 study found that surgery significantly improved survival for patients with epithelioid tumors, adding more than six months to their median life expectancy. However, for patients with sarcomatoid tumors, there was not a clear survival benefit. In this study, those with biphasic tumors also experienced a benefit, although it was smaller. Other studies have not found a benefit for surgery in patients with biphasic tumors.
Chemotherapy
A 2016 study showed that cell type has an influence on the likelihood of response to chemotherapy. Sixty-three percent of patients with epithelioid tumors showed a significant clinical response to chemotherapy, while only 45 percent of those with sarcomatoid tumors showed such a response. Although patients with epithelioid tumors showed a greater likelihood of benefit, chemotherapy is still often recommended as the first line of treatment in patients with sarcomatoid tumors, and there is a relatively good chance that they will respond to the treatment.
Other Treatment Options
This includes many patients with sarcomatoid tumors. A device called Tumor Treating Fields, which uses electrical fields passed through the skin to affect the cells’ ability to divide, is also approved for use in pleural mesothelioma patients who are not candidates for surgery.
In addition, some patients may choose to participate in a clinical trial. This is a research study of a new treatment, or a new combination of existing treatments. Participating in a clinical trial is a way for some patients to potentially gain access to a cutting-edge treatment with the potential to extend life.
If you’re interested in exploring this option, you should discuss it with your oncologist to learn more about what’s involved.