Biphasic pleural mesothelioma cancer is caused by asbestos exposure and forms in the pleura, or the lining of the lungs. Patients diagnosed with this type of mesothelioma may have varying life expectancies, because multiple types of cancerous cells are present in the body and a prognosis depends on the most prominent type of cell in each patient.
Biphasic tumors are a mix of epithelial cells, which are cube-like, with rounded edges and visible nuclei, and sarcomatoid cells, which are spindle-shaped with no visible nuclei. These two cell types typically reside in separate areas of the tumor, but they can also develop close together.
Biphasic mesothelioma is the second most common cell type of mesothelioma. About 20 to 35 percent of all malignant mesothelioma cases are biphasic. This cell type is more common in pleural mesothelioma than in other types of mesothelioma, and it is important to detect because biphasic cells can affect diagnosis and treatment.
How Is Biphasic Pleural Mesothelioma Diagnosed?
Mesothelioma is a rare cancer and can be difficult to diagnose. Symptoms aren’t easily recognizable until the cancer has progressed. The signs of mesothelioma can mirror less severe respiratory conditions, including pneumonia or asthma, which can lead to an initial misdiagnosis. By the time the cancer is diagnosed, it may have reached a later stage and spread beyond the lungs.
Detecting the cell type of mesothelioma is also difficult, and biphasic cells may be the hardest cell type to identify. That’s because epithelial cells and sarcomatoid cells often grow in separate parts of the tumor, with just one type showing up in a typical tumor sample.
To more accurately diagnose biphasic pleural mesothelioma, samples of different parts of the tumor must be collected and tested, known as a biopsy. A procedure called a thoracoscopy or video-assisted thoracic surgery (VATS) allows doctors to collect as many samples as necessary. Large tissue samples are made available if a patient undergoes surgery, which often leads to the most accurate cell type diagnosis. Larger samples can also help rule out other types of cancers that share biphasic characteristics, including synovial sarcomas and carcinosarcomas.
Biopsy samples are analyzed by pathologists, who use different tests to determine what kind of disease or cancer is present. It’s important to ensure a pathologist with extensive experience diagnosing mesothelioma is analyzing the biopsy samples if pleural mesothelioma is suspected. It is difficult to differentiate biphasic mesothelioma from epithelial mesothelioma, and the biphasic cell type can resemble other cancers, making it important to have an expert pathologist working on the biopsy samples.
The World Health Organization (WHO) recommended there should be at least 10 percent of epithelial and sarcomatoid cells present to identify biphasic mesothelioma. Pathologists point out that WHO didn’t have a consensus on the criteria or proof of clinical significance for the designation, but it remains the primary definition of biphasic mesothelioma. It is relatively common for biphasic mesothelioma to contain less than 50 percent desmoplastic cells, which are a subtype of sarcomatoid cells.
A technique called immunohistochemistry can help to accurately distinguish biphasic pleural mesothelioma from other forms of cancer by identifying certain proteins in cells. For example, immunohistochemical tests that reveal proteins called cytokeratins are helpful at identifying sarcomatoid cells. However, the more differentiated or different the cells appear, the less helpful immunohistochemistry is at diagnosing the cell type. Meaning that immunohistochemistry is more helpful for biphasic tumors that are predominately composed of either epithelial or sarcomatoid cells.
How Biphasic Cells Affect Pleural Mesothelioma Treatment and Prognosis
Mesothelioma treatment is generally more dependent on the stage and location of the tumor and less dependent on the type of cells that are present. This means biphasic pleural mesothelioma patients may still be eligible for the common treatments for mesothelioma, including chemotherapy, radiation therapy and surgery.
However, cell type can determine the aggressiveness of the treatment plan. Epithelial cells generally respond better to treatment than sarcomatoid cells, which means patients with more epithelial cells in a biphasic mix have a slightly better prognosis. Not every biphasic pleural mesothelioma patient will receive the same type of treatment.
Because of the rare nature of mesothelioma, it’s important for patients to find a mesothelioma specialist to guide their care, determine their cell type and create a treatment plan. The Pleural Mesothelioma Center employs experienced Patient Advocates who can help you locate a doctor who can create a plan unique to your diagnosis.