Mesothelioma Cell Types

Summary

Mesothelioma has three primary types of cells: epithelioid, sarcomatoid or biphasic. If diagnosed with mesothelioma, it’s important to understand which cell type your tumors are made of, as each type responds to treatment differently. Mesothelioma specialists factor in cell type when determining therapy options. Cell types can also impact your quality of life, length of life, and overall prognosis.

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 mesothelioma cells.

Researchers have identified three primary mesothelioma cell types—epithelioid, sarcomatoid, and biphasic cells—which are cell classifications based on characteristics observed under a microscope.

Mesothelioma specialists will use a biopsy to determine the type of cell a tumor is comprised of, studying tissue samples to 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 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 will qualify for the multimodal approach, and you may be referred to chemotherapy or clinical trials instead.

Epithelioid Cell Subtypes

The follow are epithelioid cell subtypes—further classifications of behaviors and characteristics of epithelioid tumors:

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 growth in a patient’s genital glands and spread from there. However, they can also appear sporadically in other parts of the body as well.

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

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 and is highly unlikely to become malignant. In fact, cystic mesothelioma has only resulted in 1 reported death and therefore may have the highest survival rate of all mesothelioma types.

Deciduoid:  Deciduoid cells were initially found in individuals who hadn’t encountered asbestos, with asbestos-related cases discovered at later. 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 and, because mesothelioma cases are so rare, scientists are still trying to determine whether mesothelioma small cells behave the same way in mesothelioma as they do in lung cancer, lymphoma, and other conditions.

Sarcomatoid Mesothelioma Cells

Sarcomatoid cells are the rarest of the three major mesothelioma cell types and are 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, spreading 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 combated using surgery and chemotherapy. While these treatment options were not particularly effective in the past, recent advancements in chemotherapy cocktails 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:

Desmoplastic – One of the more common sarcomatoid subtypes, desmoplastic mesothelioma is found in 5-10% of pleural mesothelioma cases. Unfortunately, it is 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: Similar to osteosarcomatous, chondrosarcomatous occurs when spindle-shaped cartilage cells grow within the mesothelium.

Biphasic Mesothelioma Tumors

Biphasic cells are the classification 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.

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.

Other Rare Mesothelioma Cell Types

In addition to the three most common mesothelioma cell types, there are several 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 that 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 pleural, peritoneal, or pericardial locations and is typically treated with traditional techniques. The majority of heterologous mesothelioma cells are found in sarcomatoid subtypes, although 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 cell type, then it’s important to seek the second opinion of a mesothelioma specialist.

Doctors can misdiagnose cell types, which can limit your 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. Our Patient Advocates can help you learn more about choosing the right mesothelioma specialist for your diagnosis.

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Last modified: February 2, 2018