Mesothelioma Cell Types

Mesothelioma tumors are made up of several different types of cells, including epithelioid and sarcomatoid. Biphasic tumors have both cells present. Each of these has its own treatment. Cell types can also impact your quality of life, length of life and overall prognosis.

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Determining Mesothelioma Cell Type

Mesothelioma researchers are still trying to understand how and why mesothelioma cells form in some patients and not others, but they know that mesothelioma cells follow similar growth and division patterns to other types of cancer cells.

Molecular interactions can cause cells to stop following the body’s normal growth patterns and develop tumors (cancerous tissues masses) of genetically mutated cells instead. When these mutated cells originate or occur in the lining of the abdomen, lungs or heart — called the mesothelium — they are considered to be mesothelioma cells.

Researchers have identified two primary mesothelioma cell types — epithelioid and sarcomatoid — which are cell classifications based on characteristics observed under a microscope. When a tumor has both cells present, it is known as a biphasic tumor.

Mesothelioma specialists will use a biopsy to determine the type of cell that is present, which can help them confirm the diagnosis. From here, mesothelioma specialists can make confident decisions on which treatment paths to explore.

Epithelioid Mesothelioma Cells

Epithelioid cells are the most common type of mesothelioma cell and the easiest to treat. These cells are characterized by their defined, uniform appearance, a single nucleus, and their slower growth patterns.

Epithelial Cells and Mesothelioma

Epithelial cells divide quickly but also lump together, building upon themselves as they spread through the body. Researchers estimate that more than half of mesothelioma cases are caused by epithelioid cells.

Epithelioid cells are often treated using a multimodal approach that combines surgery, chemotherapy, and radiation treatments. However, not all patients with epithelioid mesothelioma qualify for the multimodal approach, and you may be referred to chemotherapy or clinical trials instead.

Epithelioid Cell Subtypes

Mesothelioma specialists classify epithelioid cells into special classifications and behaviors.

Epithelioid cell subtypes include:

Adenomatoid/Glandular

Recognized by its origins within the body’s glands, adenomatoid or glandular mesothelioma is a rare subtype of epithelioid mesothelioma. Adenomatoid cells usually begin in a patient’s genital glands and spread from there. However, they can also appear sporadically in other parts of the body.

To further complicate matters, adenomatoid cells can be either benign or malignant, making it hard for doctors to determine the severity of cancer. Adenomatoid cells don’t always involve mesothelium tissue, which means it’s possible to have malignant adenomatoid cells that aren’t mesothelioma.

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Cystic

With fewer than 200 cases of cystic mesothelioma reported worldwide, the global understanding of this epithelioid subtype is fairly limited. Fortunately, cystic mesothelioma is benign (non-cancerous) and highly unlikely to become malignant (cancerous). In fact, cystic mesothelioma has only resulted in 1 reported death and may have the highest survival rate of all mesothelioma types.

Deciduoid

Deciduoid cells are recognized by their large polygon or oval shapes and well-defined borders. These cells are often a particularly aggressive epithelioid subtype.

Papillary/Well-Differentiated Papillary Mesothelioma

Papillary mesothelioma, also referred to as well-differentiated papillary mesothelioma (WDPM), is a rare form of benign mesothelioma. Papillary mesothelioma often isn’t linked to asbestos exposure, which makes it a unique and intriguing form of mesothelioma.

In addition, there is no clear treatment for papillary mesothelioma, although surgery, chemotherapy or radiation are all potential options.

Small Cell

Small cells are most commonly found in the abdomen but can also occur in the heart and lungs. Small cells can also be found in several types of cancer unrelated to mesothelioma.

Because mesothelioma cases are so rare, scientists are still trying to determine whether mesothelioma small cells behave the same as they do in lung cancer, lymphoma, and other conditions.

Sarcomatoid Mesothelioma Cells

Sarcomatoid cells are the rarest of the 3 major mesothelioma cell types and the most challenging to treat. Microscopic sarcomatoid cells are identified by their large size and spindle shape, typically combined in fibrous-looking bundles.

In some instances, sarcomatoid cells will have more than one nucleus. Sarcomatoid cells don’t form masses like epithelioid or biphasic cells and are more likely to present as small nodules that spread quickly throughout your body.

Sarcomatoid cells are considered the most aggressive type of mesothelioma cell and are difficult to diagnose accurately.

Biopsy samples may be too small to properly test, and these cells look similar to many other forms of cancer. Sarcomatoid cells are traditionally treated using surgery and chemotherapy. While these treatment options were not particularly effective in the past, recent advancements in chemotherapy drug combinations suggest it may be a viable treatment option in the future.

Sarcomatoid Cell Subtypes

The following cell subtypes are most commonly found in sarcomatoid cells, but some have also occurred in epithelioid and biphasic cells.

Sarcomatoid cell subtypes include: 

Desmoplastic: One of the more common sarcomatoid subtypes, desmoplastic mesothelioma is found in 5-10% of pleural mesothelioma cases. Unfortunately, it’s one of the more challenging subtypes to diagnose and often has a poor prognosis.

Lymphohistiocytoid: When cells that are typically found within the immune system bundle together in the mesothelium, the resulting condition is lymphohistiocytoid mesothelioma.

Osteosarcomatous:  This extremely rare subtype of sarcomatoid mesothelioma occurs when cancerous bone cells are located in the mesothelium.

Chondrosarcomatous: The chondrosarcomatous cell subtype occurs when spindle-shaped cartilage cells grow within the mesothelium.

Biphasic Mesothelioma Tumors

A tumor is considered to be biphasic given when both epithelioid and sarcomatoid cells are found together and are sometimes referred to as “mixed mesothelioma.” The prominence of one cell type over the other will help determine how the cancer behaves — whether it clumps and spreads slowly like epithelioid cells, or takes over the body quickly like sarcomatoid cells.

Treating Biphasic Mesothelioma

Biphasic cases with higher percentages of sarcomatoid cells are more challenging to treat than those with lower percentages, simply because sarcomatoid cells are more aggressive and resilient than epithelioid cells.

If you’ve been diagnostic with biphasic mesothelioma, your doctor is likely to suggest surgery, chemotherapy, and radiation therapy, if it’s a viable option.

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Other Rare Mesothelioma Cell Types

In addition to the 3 most common mesothelioma cell types, there are a few additional subtypes that have been recognized. It’s also possible that additional subtypes exist and have yet to be discovered.

Some of the known rare subtypes include:

Benign: The vast majority of mesothelioma forms are malignant, which means the cells are cancerous and spread throughout the body. However, a form of non-cancerous, benign mesothelioma has also been identified in some extraordinarily rare cases.

Benign mesothelioma is not dangerous in itself, but can be a precursor to malignant mesothelioma and needs to be monitored carefully.

Heterologous:  This extremely rare subtype of mesothelioma combines numerous types of cells into a single tumor. For example, heterologous mesothelioma may also contain cells typically found in bones and other parts of the body that don’t relate to the mesothelium.

Heterologous mesothelioma can be found in any type of mesothelioma and is typically treated with standard treatments. The majority of heterologous mesothelioma cells are found in sarcomatoid subtypes, although an instance has also been reported in biphasic and epithelioid cells.

Seeking Treatment for Your Mesothelioma Cell Type

If you’ve been diagnosed with epithelioid, sarcomatoid or biphasic mesothelioma, then it’s important to seek the second opinion of a mesothelioma specialist.

Doctors can misdiagnose cell types, limiting your mesothelioma treatment options. Obtaining an accurate cell type diagnosis ensures you get the most effective treatments that can help improve your life expectancy.

For more information about getting mesothelioma treatment, contact the Mesothelioma Justice Network today. We can help you learn more about choosing the right mesothelioma specialist for your diagnosis.

Author:Stephanie Kidd

Editor-in-Chief of the Mesothelioma Justice Network

Stephanie Kidd

Stephanie Kidd works tirelessly as a dedicated advocate for the vulnerable and underrepresented. Stephanie worked as a copywriter for an agency whose focus was communicating safety procedures on construction work sites. With her extensive background in victim advocacy and a dedication to seeing justice done, Stephanie works hard to ensure that all online content is reliable, truthful and helpful.

Last modified: July 3, 2019

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