Mesothelioma develops when inhaled or ingested asbestos fibers irritate healthy tissue cells, mutating them into cancerous cells. Mesothelioma cells develop in different ways and can be classified as either epithelioid, sarcomatoid, or biphasic (mixed). Getting an accurate cell type diagnosis is critical to receiving the best treatment options possible.
What Are the Different Mesothelioma Cell Types?
Mesothelioma is a form of cancer caused when healthy cells in the mesothelium mutate after asbestos gets lodged in the body’s tissue. Over time, these healthy cells become irritated and transform into mesothelioma cancer cells.
Depending on the patient, mesothelioma cells can develop in different ways, with various shapes, sizes, and cellular behaviors.
These characteristics are what determine a patient’s cell type, and accordingly, how that patient should be treated.
The 3 mesothelioma cell types are:
Doctors determine a patient’s mesothelioma cell type by collecting tissue biopsy samples and then analyzing the cells under a microscope. Pathologists will compare the samples to existing cell profiles to identify the cell type a patient has.
Mesothelioma cell types have a significant impact on life expectancy and treatment plans, as some cell types are more treatable than others. Epithelioid cells are the most common type and are the easiest to treat. Sarcomatoid and biphasic cells grow more aggressively, making them difficult to treat.
Fortunately, treatment options are available for all types of mesothelioma cells. New technologies and advancements are improving the prognosis for all types of mesothelioma, as mesothelioma specialists continually break ground on new treatment options.
Veterans with mesothelioma can seek medical care through the VA and other health care centers across the country. Mesothelioma treatment centers have teams of specialized medical professionals on staff who can develop personalized treatment options for veterans.
Epithelioid mesothelioma is the most common cell type of mesothelioma. It makes up about 50-70% of all cases.
Epithelioid cells are most commonly found in cases of pleural mesothelioma (develops in the lining of the lungs), although they can also be present with peritoneal mesothelioma (develops in the lining of the abdomen) or pericardial mesothelioma (develops in the lining of the heart).
Epithelioid mesothelioma occurs when healthy epithelial cells mutate. Epithelial cells line the tissues of organs, glands, and the skin and exist in almost every part of the body. Epithelial cells have a variety of purposes — they protect the tissues from microbes and contaminants, act as receptors for the brain, and transport nutrients and energy through the body.
Epithelioid mesothelioma has a better survival rate than other mesothelioma cell types. Because of their prominence in cases of mesothelioma, most historic mesothelioma research and resources have focused on defeating this cell type.
Epithelioid cells have the following characteristics:
- Defined nuclei (cell center)
- Cuboid shape
- Clumped formation
- Slower growth than other cell types
Epithelioid cells are also the easiest form of mesothelioma to treat, due to their slower spread. As a result, epithelioid mesothelioma has the best prognosis.
Diagnosing Epithelioid Mesothelioma
Epithelioid mesothelioma is diagnosed in two stages. First, the oncologist (cancer doctor) orders CT or MRI scans of the patient’s chest. Then, if mesothelioma or another form of cancer is suspected, they perform a biopsy.
A common biopsy procedure is a thoracoscopy, which is a way to see the lung tissue using a camera and a flexible tube. A surgical or needle biopsy may be performed instead when a direct path to the affected area is available. In both cases, collected samples are sent to a pathology lab for examination.
Epithelioid cells can look like other types of cancer, so pathologists use a microscope to examine the tissue samples. They compare existing samples and use their expertise to determine what cell type the patient has. The information is then presented in a report to the patient’s doctor.
Although the process can be stressful, it’s essential. Epithelioid cells mimic other types of cancer, and doctors must confirm a mesothelioma diagnosis to give patients their best chance of increasing survival.
Epithelioid Mesothelioma Life Expectancy and Survival Rates
Epithelioid mesothelioma has the best survival rate because it is the most common and best-understood type of mesothelioma. As a result, cancer researchers have spent the most time researching and treating epithelioid mesothelioma.
Epithelioid cells also mutate and spread slower than sarcomatoid or biphasic cells, which makes this form of mesothelioma easier to treat and manage. Aggressive cancer cells often spread faster than treatment can contain them, but that isn’t always the case with epithelioid cells.
A 2017 study looked at 19 patients with advanced epithelioid cells that hadn’t spread to nearby lymph nodes. Each patient had stage 3 or 4 malignant pleural mesothelioma, which has a median survival of 16 and 12 months, respectively.
The patients received pleurectomy with decortication surgery to remove their tumors, and their overall survival increased to over 7 years — approximately 7 times longer than the average survival time.
Sarcomatoid mesothelioma cells are spindle-shaped and look like the cells of bone and soft-tissue cancers called sarcomas. Instead of clumping, the cells form a thin, fibrous sheet on the body’s linings. Because of this distinct cell appearance, sarcomatoid mesothelioma is also known as “spindled mesothelioma” and “diffuse malignant fibrous mesothelioma.”
Sarcomatoid cells are the least common type of mesothelioma cell, only found in 7-20% of mesothelioma cases. Sarcomatoid cells can be present in either pleural or peritoneal mesothelioma cases and, like all forms of mesothelioma, the cells grow and spread in tissue lining.
Sarcomatoid cells have the following characteristics:
- Long, large, and spindle-shaped
- Large nuclei
- Fast growth compared to other cell types
Sarcomatoid mesothelioma is the most challenging type of mesothelioma to treat. The cells spread quickly, and because they form a thin, sheet-like mass, sarcomatoid tumors are difficult to remove. Sarcomatoid mesothelioma is also hard to diagnose in its early stages and is typically only discovered after the cells are well-established, making cancer treatment even more challenging.
Diagnosing Sarcomatoid Mesothelioma
Sarcomatoid mesothelioma cells look similar to other types of sarcoma cancers, which makes them difficult to identify and diagnose accurately. Even under a microscope, sarcomatoid cells can easily be mistaken for an incorrect cancer type.
Doctors begin their diagnosis using the same techniques as other forms of mesothelioma. First, the patient receives CT scans of the chest or MRI scans. If the scan suggests cancer may be present, the doctor takes a biopsy. After that, doctors examine the sample under a microscope to see what kind of cancer it is.
If sarcomatoid mesothelioma is suspected, doctors may use immunohistochemistry to confirm the diagnosis. Immunohistochemistry is a test that looks for antibodies specific to sarcomatoid mesothelioma. Pathologists use special stains that stick to known antibodies, making microscopic examination more accurate. If the mesothelioma antibodies are found, the diagnosis can be confirmed.
Doctors must do their diligence when performing these tests to prevent misdiagnosis. Sarcomatoid mesothelioma is frequently misdiagnosed, which can lead to ineffective treatment strategies and unnecessary patient suffering.
Sarcomatoid Mesothelioma Survival Rates and Life Expectancy
Sarcomatoid mesothelioma has a worse survival rate than epithelioid mesothelioma because sarcomatoid cells are very aggressive and spread quickly. While many cancer cells clump together, sarcomatoid cells form a thin lining that allows them to expand throughout the body rapidly.
Sarcomatoid mesothelioma is also less common than epithelioid mesothelioma, resulting in fewer research opportunities for doctors to learn to identify them. Sarcomatoid mesothelioma is less recognized and understood than other cancers, which makes it more challenging to treat.
Studies suggest that the median survival rate for sarcomatoid mesothelioma is about 6 months. However, half of all patients live past this median, and the treatment received is a strong determinant of survival time.
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Biphasic mesothelioma occurs when a patient has both epithelioid and sarcomatoid cells in the same tumor. As with all mesothelioma cells, biphasic cells are triggered when healthy cells are exposed to asbestos fibers.
Biphasic mesothelioma is the second most common kind of mesothelioma and makes up 20-35% of all mesothelial cancers. These cells are primarily found in pleural mesothelioma cases, but biphasic cells can also be present in other mesothelioma locations.
A biphasic tumor’s development depends on which cell type is more dominant. Biphasic mesothelioma that’s dominated by epithelioid cells will take on the behavior and characteristics of epithelioid cells, while tumors dominated by sarcomatoid cells will act like sarcomatoid mesothelioma.
Doctors must take care to accurately diagnose and treat biphasic mesothelioma properly because of its mixed cells. Treatment and quality of life planning must consider both cell types.
Diagnosing Biphasic Mesothelioma
Diagnosing biphasic mesothelioma can be difficult. Biopsy samples only observe a small piece of a tumor at a time, while epithelioid and sarcomatoid cells may be far apart on a biopsy sample. Pathologists may miss the biphasic aspect of the condition if they only see one cell type under the microscope.
Due to these challenges, doctors may need to collect large samples of a tumor to identify biphasic mesothelioma. Larger samples give a better view of the overall cell landscape and can help pathologists make a more accurate diagnosis. However, If the doctor doesn’t suspect biphasic mesothelioma, large samples may never be collected.
In some mesothelioma cases, people only find out they have biphasic mesothelioma after surgery. Surgery provides the best access possible to many tumors, and surgically removed tumors are often collected and analyzed to reconfirm a patient’s diagnosis.
Biphasic Mesothelioma Life Expectancy and Survival Rates
Most patients with biphasic mesothelioma have a median survival time of around 12 months. However, survival times greatly depend on the ratio of epithelioid and sarcomatoid cells present in the patient’s tumor.
Patients with more epithelioid cells tend to have a better prognosis, with their life expectancy improved by months or even years. Conversely, patients with a higher ratio of sarcomatoid cells tend to have a lower prognosis, as the more aggressive cells spread faster.
How quickly a patient is diagnosed also plays a significant role in the life expectancy for patients with biphasic mesothelioma. Like all mesothelioma cases, earlier diagnosis tends to lead to better results. The sooner a patient receives treatment, the better the outcome.
Treating Your Cell Type
Mesothelioma treatments can improve the survival time and quality of life for patients with any mesothelioma cell type. Patients should work closely with their doctors to determine the best treatment strategy for their cell type and stage, while also considering personal wishes.
The most common treatment for mesothelioma is a combination of surgery, chemotherapy, and radiation. This treatment strategy, called the tri-modal approach, gives patients the best chance possible at fighting their disease. Surgery is used to remove all visible signs of a tumor, while chemotherapy and radiation fight at the cellular level.
However, the cell type may determine the type of treatment received. Surgery is often the best way to improve mesothelioma life expectancy, but it’s not ideal for all cases.
Doctors and surgeons consider the disease stage when determining whether a patient is eligible for surgery. Most surgeons consider mesothelioma patients with stages 1, 2, and 3 to be potentially operable, while surgery may not be an option in later stages. Because sarcomatoid cells spread faster, the cancer can advance more quickly into these later stages.
When developing a treatment strategy, surgeons also consider resectability — the likelihood a surgeon can remove most of the mesothelioma tumors. A patient’s cell type can greatly impact whether their mesothelioma is resectable, as epithelioid cells are easier to operate on. Unfortunately, not all tumors can be removed.
According to the American Cancer Society, “Whether or not the cancer can be removed depends not only on how far the tumor has grown, but also on its subtype (most doctors believe only epithelioid and mixed/biphasic tumors are potentially resectable), where it is located, and if the patient is healthy enough to have surgery.”
Here are some other important health factors that make a patient more eligible for surgical treatment:
- Good overall health
- Ability to continue daily life normally
- Younger age
- No chest pain
- Little weight loss
- Normal red and white blood cell counts
- Normal blood platelet counts
Epithelioid cells tend to allow more treatment options than sarcomatoid cells, but treatments — including surgery — may still be an option for all patients. Patients with any cell type should work with mesothelioma specialists to discuss treatment options.
Finding Treatment for Your Cell Type
The best way to improve a patient’s prognosis is to seek treatment through a specialist. Mesothelioma specialists have experience treating all cell types and will tailor treatment strategies to a patient’s cell type.
Mesothelioma specialists are located in cancer centers across the country, many of which have dedicated mesothelioma programs. Doctors in these programs have decades of experience diagnosing and treating mesothelioma and may try new therapies in addition to standard treatments.
Mesothelioma programs exist at both standard medical centers and VA affiliated centers. VA centers with mesothelioma programs are specially equipped to help veterans who may be affected by mesothelioma.
The Mesothelioma Veterans Center has patient advocates who can help veterans with mesothelioma find treatment and learn about other potential benefits, including VA benefits.
To learn more about the treatment options available to you, get a Free Mesothelioma Veterans Packet.