What is Biphasic Mesothelioma?
When a case of mesothelioma (a rare cancer found in the chest and abdominal cavities) is diagnosed, doctors will examine tissue samples to determine which of the three mesothelioma cell types are present – epithelioid, sarcomatoid or biphasic. Cell type is an important part of the overall mesothelioma diagnosis. This variable plays a large role in which treatment or treatment combinations are administered, as each cell type displays unique cellular characteristics and behaviors.
Biphasic or mixed mesothelioma cell type is the second most common cell type. After epithelioid and before sarcomatoid. Biphasic cell type contains both epithelioid and sarcomatoid cells and accounts for around 30-40% of all cases of mesothelioma.
To be diagnosed as biphasic cell type, at least 10% of the tumor mass needs to be either epithelioid or sarcomatoid cells.
Biphasic mesothelioma is unique as it displays the cellular characteristics and behaviors of both epithelioid and sarcomatoid cells. Treatment and prognosis of biphasic cell type depend on which cell type is most prominent, with higher accounts of epithelioid cells offering more treatment options and a better prognosis.
Biphasic mesothelioma is commonly misdiagnosed as epithelioid and sarcomatoid cells grow in different areas of tumors. Multiple samples from different parts of the tumor need to be taken and studied to identify both cell types. Finding only epithelioid or sarcomatoid cells in biphasic mesothelioma can have negative outcomes as incorrect treatment plans can be administered and worsen a patient’s prognosis.
For doctors to develop a proper treatment plan, they need to understand the characteristics, behavior and chemistry of the mesothelioma cell type. Doctors will study tissue samples (biopsy) to understand how fast cells are able to replicate and spread and how their cellular chemistry interacts with other tissues and cells in the body. They combine these variables to make a confident diagnosis.
Biphasic mesothelioma is the most difficult cell type to diagnose as the epithelioid and sarcomatoid cells appear in different areas of the tumor and are frequently missed when collecting tissue samples. To properly diagnose biphasic mesothelioma, multiple samples need to be taken from different parts of the tumor and tested. To achieve the most accurate diagnosis, large tissue samples can be collected via surgery.
Biphasic mesothelioma is also commonly misdiagnosed as carcinosarcomas—cancers that contain a mixture of both epithelial and connective tissue cells. It can also be misdiagnosed as synovial sarcoma—a rare form of cancer that develops in soft tissue found in the arms and legs. For these reasons, multiple protein tests, also known as immunohistochemistry, need to be conducted to appropriately diagnose biphasic tissue samples, ensuring proper treatment.
How a cell behaves, especially the rate at which it replicated and spreads, can have large implications on disease prognosis. It is important to understand which ratio of epithelioid and sarcomatoid cells exist in a biphasic tumor, as life expectancy and survival rates are better with higher proportions of epithelioid cells rather than sarcomatoid.
Biphasic mesothelioma that is epithelioid-dominant will appear in varying degrees of organized masses, depending on how early the cancer was found. The square epithelioid cells tend to replicate quickly, but in doing so, they pile on top of each other forming masses that prevent them from spreading quickly around the body.
When sarcomatoid cells account for the largest proportion of biphasic tumors, the cellular behavior is very different. Sarcomatoid cells will grow sporadically across the lining of an organ or cavity in small lumps. These cells rarely form masses, which means they have a higher chance of spreading to surrounding tissues.
When viewed under a microscope, biphasic mesothelioma takes on the cellular characteristics of either epithelioid or sarcomatoid cells—whichever cell type is dominant. If a large proportion of the biphasic tumor contains sarcomatoid cells, then microscopic samples of biphasic mesothelioma will contain large cells that appear spindle-shaped.
Sarcomatoid cells can sometimes be viewed as fibrous-looking bundles with more than one nuclei—the cellular structures that are responsible for holding a cell’s DNA. Alternatively, if the biphasic tumor is predominately made up of epithelioid cells, the biphasic tissue sample will be characterized by cells that are cube-like, uniform in appearance and with a well defined single nucleus.
Treatments for Biphasic Mesothelioma
In cases of mesothelioma, treatment decisions can be determined by cell type diagnosis. As biphasic is the most frequently misdiagnosed cell type, is important to ensure tissue samples are extensively studied by pathologist specialists (doctors who study diseased cells).
Once accurately diagnosed, patients with biphasic mesothelioma are treated with surgery, radiation therapies and chemotherapy. The detailed nature of the treatment plan is impacted by the portion of epithelioid and sarcomatoid cells that are found in the biphasic tumor.
Biphasic mesothelioma may respond well to treatment if the tumor contains mostly epithelioid cells, as this cell type responds best to treatment. However, if a biphasic tumor contains more sarcomatoid cells than epithelioid cells, treatment options may be more limited.
Epithelioid-dominant biphasic mesothelioma can be treated with surgery, radiation therapy and chemotherapy. More aggressive types of treatment are generally recommended for epithelioid subtypes to improve prognosis. Sarcomatoid-dominant variations of biphasic mesothelioma are more challenging to treat, as the cells do not grow as masses, making them harder to isolate during surgery and radiation therapy. Multiple rounds of chemotherapy can sometimes be effective in treating sarcomatoid cells.
Treatments for biphasic mesothelioma will differ based on patient age, overall health and medical history. Tumor location and size all have varying impacts. An important note needs to be made that new treatment options are constantly being developed, leading to better prognosis for biphasic mesothelioma in the future.
Biphasic Mesothelioma Prognosis
Prognosis is a medical term describing the possibility of a patient’s recovery based on the likely disease course. Factors like the patient’s overall health, age, gender, tumor location, and cancer stage are taken into life expectancy and survival rate considerations.
When determining a prognosis for mesothelioma, cell type is another variable that is used to predicting a prognosis. In order to achieve the most favorable prognosis, extensive tests need to be performed to accurately diagnose biphasic cell type to ensure the best treatment plan is developed.
Research has shown that survival rate for biphasic mesothelioma is more favorable than sarcomatoid cell type, but less favorable when compared to epithelioid. The median (average) life expectancy is between 11 and 15 months, with better prognosis generally associated with biphasic tumors with higher proportions of epithelioid cells rather than sarcomatoid.
Life expectancy and survival rates have been shown to be more favorable when biphasic cases are caught at an earlier stage, or when tumors are located in the abdomen cavity instead of inlining of the chest and heart.
Biphasic Cell Subtypes
Epithelioid and sarcomatoid cell types can be further classified into subtypes that have varying cellular characteristics and behaviors. In the case of biphasic mesothelioma, it is possible for epithelioid and sarcomatoid subtypes to be found within tumor samples. These subtypes can give doctors further insight into how biphasic mesothelioma may react to varying forms of treatment.
Getting a Second Opinion on Biphasic Mesothelioma
Mesothelioma is a rare and complex disease. It’s possible for mesothelioma tumors to be composed of two different mesothelioma cell types—sarcomatoid and epithelioid—each with their own subtypes. Doctors need to know which cell type is involved to put together the most effective treatment plan and communicate realistic expectations to patients.
If you’ve been diagnosed with mesothelioma, you deserve specialized care delivered by leading medical experts. For more information on seeking a second opinion and obtaining an accurate mesothelioma diagnosis, contact our Victim Advocates today.