Biphasic mesothelioma is a mixture of epithelioid and sarcomatoid cells. For a tumor to be diagnosed as biphasic, each cell type must represent at least 10%. This is more common in cases of pleural mesothelioma. A higher percentage of sarcomatoid cells indicates a more aggressive cancer.
What is biphasic mesothelioma?
Biphasic malignant mesothelioma is the second most common type of cell in the disease.
The life expectancy of patients with this form of cancer varies because the prognosis depends on the ratio of epithelial and sarcomatoid cells.
The higher the percentage of sarcomatoid cells, the worse the prognosis.
This type of cell is more common in pleural patients than in peritoneal patients.
Understanding the features and diagnosis of this type of mesothelioma can help you make informed treatment decisions with your doctor.
In biphasic cases, epithelioid cells and sarcomatoid cells may exist close to each other. They can also appear in separate areas of a tumor.
These cell types are important to detect because some clinical trials and treatments target specific cell types. The characteristics of your cell type do not affect your symptoms. They can only affect your life expectancy by a few months.
Epithelioid mesothelioma has round, cube-shaped cells with long, thin microvilli, which are small, hair-like protuberances in the cell membrane.
Biphasic mesothelioma is often called a “mixed” cell type because it contains cells from both types of mesothelioma cells.
Sarcomatoid mesothelioma consists of spindle-shaped cells arranged in a disorganized manner.
This type can be difficult to detect and diagnose.
In a key diagnostic test, called a biopsy, physicians may collect only a small sample of tissue to be studied in the laboratory.
Sampling at one location provides limited insight into the type and amount of mesothelioma cells involved.
Physicians can make a more accurate diagnosis by taking tissue samples from several parts of the tumor. Determining the specific cell type is important for the diagnostic process as it can affect your treatment options and your prognosis.
Prevent a wrong diagnosis
Doctors use advanced tests, such as immunohistochemistry, to distinguish biphasic mesothelioma from other diseases that are easily confused with this cancer. This technique can detect certain proteins, revealing the specific type of abnormal cells.
With this information, physicians can rule out common diagnostic errors, including cancers such as synovial sarcoma and carcinosarcoma.
A recent study published in the Journal of Thoracic Oncology found that the biphasic type could be misdiagnosed after a biopsy. A total of 83 patients participating in the study were confirmed to have this type of pleural cancer after undergoing extensive surgery called extra-pleural pneumonectomy.
However, only 26% of these patients were originally diagnosed with this subtype. The authors explained that biphasic mesothelioma could be diagnosed more accurately after surgery. Initial diagnostic methods included thoracoscopy, thoracotomy, computed tomography, and other biopsy methods.
Patients with biphasic cell type may not be considered for an aggressive treatment plan as would patients with epithelioid type.
The reason is that biphasic carries a slightly darker prognosis than the epithelioid. However, the treatment is not completely based on cell type.
Most patients follow at least one of the three most common treatments, namely:
Treatment usually depends more on the stage and location of the tumor than the type of cell involved.
The prognosis for patients with biphasic mesothelioma varies according to the ratio of epithelial and sarcomatoid cells present in each case.
In a study of 85 patients with pleural mesothelioma and with various cell subtypes, individuals in the biphasic subtype had an average survival of approximately 15 months. Those with the epithelial subtype showed the highest average survival – more than 22 months.
The researchers observed slightly better survival in biphasic patients whose tumors were predominantly epithelial cells, compared to those with mostly sarcomatoid cells. While the survival advantage was only 16 days, sarcomatoid cells are less sensitive to treatment than epithelial cells. As a result, biphasic patients with fewer sarcomatoid cells tend to perform better with treatment.