Biphasic Mesothelioma: Prognosis, Cell Type, and Treatment Options

Biphasic mesothelioma is a subtype of malignant mesothelioma that contains a mixture of two different cancer cell types. It is less common than epithelioid mesothelioma but more common than purely sarcomatoid mesothelioma. Because biphasic mesothelioma combines features of both cell types, its behaviour, treatment response, and prognosis fall somewhere between the two.

For patients and families, a diagnosis of biphasic mesothelioma often raises complex questions. Outcomes can vary widely depending on the proportion of each cell type present, where the cancer is located, and how advanced the disease is at the time of diagnosis. Understanding what biphasic mesothelioma means and how it differs from other forms of mesothelioma is critical for informed decision making.

What is biphasic mesothelioma

Biphasic mesothelioma is defined by the presence of both epithelioid cells and sarcomatoid cells within the same tumour. To be classified as biphasic, each cell type must make up at least a portion of the tumour, typically with a minimum threshold used by pathologists during diagnosis.

Epithelioid cells tend to grow in a more organized pattern and usually respond better to treatment. Sarcomatoid cells are more aggressive, grow more irregularly, and are more resistant to therapy. However, newer immunotherapy drugs have shown activity against sarcomatoid mesothelioma, offering meaningful benefit for some patients where traditional treatments have been limited. Biphasic mesothelioma contains elements of both, which is why its clinical behaviour can differ significantly from patient to patient.

This subtype accounts for roughly 20 to 30 percent of mesothelioma cases. It can occur in the lining of the lungs, abdomen, heart, or testicles, though it is most commonly diagnosed in pleural mesothelioma affecting the lung lining.

Causes of biphasic mesothelioma

Like all forms of mesothelioma, biphasic mesothelioma is caused by asbestos exposure. Asbestos fibres are microscopic and durable, allowing them to lodge in the body for decades. Over time, these fibres cause chronic inflammation and cellular damage that can eventually lead to cancer.

Most exposure occurred in occupational settings such as construction, shipyards, power plants, refineries, factories, and industrial maintenance environments. Workers often inhaled asbestos fibres without knowing the risks, as many employers failed to provide warnings or protective equipment.

Secondary exposure also occurred when fibres were carried home on clothing, exposing family members. Many of our female clients were exposed through their spouse or parents. The long latency period between exposure and diagnosis, often 20 to 50 years, makes it difficult for patients to immediately identify the source of exposure.

Where biphasic mesothelioma develops

Biphasic mesothelioma can develop wherever mesothelioma occurs, but its most common location is the pleura, the lining surrounding the lungs. Pleural biphasic mesothelioma typically causes respiratory symptoms and is often diagnosed after imaging reveals abnormalities in the chest.

Peritoneal biphasic mesothelioma affects the abdominal lining and may cause digestive symptoms such as abdominal pain, swelling, and changes in bowel habits. Less commonly, biphasic mesothelioma may develop in the pericardium around the heart or the tunica vaginalis surrounding the testicles.

The location of the disease influences symptoms, treatment options, and overall prognosis, even when the cell type is the same.

Symptoms of biphasic mesothelioma

Symptoms of biphasic mesothelioma vary depending on tumour location and disease progression. Early symptoms are often vague and easily mistaken for more common conditions.

In pleural cases, symptoms may include shortness of breath, chest pain, persistent cough, fatigue, and fluid buildup around the lungs. In peritoneal cases, patients may experience abdominal swelling, pain, nausea, loss of appetite, and unexplained weight loss.

As the disease advances, symptoms tend to worsen and may significantly interfere with daily life. Because biphasic mesothelioma contains aggressive sarcomatoid components, progression can sometimes be faster than in purely epithelioid cases.

How biphasic mesothelioma is diagnosed

Diagnosis of biphasic mesothelioma begins with imaging studies such as CT scans or MRIs to identify abnormalities in the mesothelium. If mesothelioma is suspected, a biopsy is required to confirm the diagnosis and determine the cell type.

Pathologists examine tissue samples under a microscope to identify the presence and proportion of epithelioid and sarcomatoid cells. Immunohistochemical testing is often used to distinguish biphasic mesothelioma from other cancers with similar features. Diagnostic confirmation typically requires biopsy and immunohistochemical testing, as outlined by the National Cancer Institute.

Accurate diagnosis is essential because treatment planning and prognosis depend heavily on cell type. In some cases, small biopsy samples may not fully capture the tumour’s complexity, which can complicate diagnosis.

The importance of cell ratio in biphasic mesothelioma

One of the defining factors in biphasic mesothelioma is the ratio of epithelioid to sarcomatoid cells. Tumours with a higher percentage of epithelioid cells tend to behave more like epithelioid mesothelioma and are often associated with better outcomes.

Conversely, tumours dominated by sarcomatoid cells are more aggressive and less responsive to treatment. Even within the biphasic category, prognosis can vary widely depending on this balance.

This variability explains why survival statistics for biphasic mesothelioma are less predictable than for other subtypes.

Treatment options for biphasic mesothelioma

Treatment options for biphasic mesothelioma depend on disease location, stage, overall health, and the proportion of epithelioid cells present. While there is no cure for mesothelioma, treatment may extend survival and improve quality of life.

Surgery may be considered in selected cases, particularly when the disease is diagnosed at an earlier stage and the epithelioid component is significant. However, surgery is less commonly an option than in purely epithelioid mesothelioma due to the aggressive nature of sarcomatoid cells.

Chemotherapy is commonly used to slow tumour growth and manage symptoms. Response rates vary, with better outcomes generally seen in cases with a higher epithelioid cell proportion. Radiation therapy may be used for symptom control or targeted tumour reduction in certain situations.

Supportive and palliative care plays a crucial role at all stages of treatment, helping manage pain, breathing difficulties, and fatigue.

Prognosis and life expectancy

The prognosis for biphasic mesothelioma is generally less favourable than for epithelioid mesothelioma but better than for purely sarcomatoid mesothelioma. Median survival times are often measured in months to a few years, depending on individual circumstances.

Key factors affecting prognosis include stage at diagnosis, tumour location, cell ratio, age, and overall health. Patients with early stage disease and a higher percentage of epithelioid cells often experience better outcomes.

It is important to remember that prognosis statistics are averages based on historical data. Individual outcomes can vary significantly, and some patients exceed expected survival times with appropriate care.

Why biphasic mesothelioma is challenging to treat

Biphasic mesothelioma presents unique challenges because it combines two biologically different cancer types. Treatments that are effective against epithelioid cells may be less effective against sarcomatoid cells, limiting overall response.

Additionally, late stage diagnosis is common, which reduces the availability of aggressive treatment options. The disease’s rarity also means that fewer clinical studies focus specifically on biphasic mesothelioma, limiting standardized treatment protocols.

These challenges highlight the importance of individualized care and realistic expectations.

Legal and financial considerations

Because biphasic mesothelioma is caused by asbestos exposure, patients and families may be eligible to pursue compensation through asbestos related claims. Cell type does not reduce eligibility for compensation, as claims are based on diagnosis and exposure rather than prognosis.

Medical documentation confirming biphasic mesothelioma and evidence of asbestos exposure are essential for these claims. Early documentation is especially important given the aggressive nature of the disease.

Compensation may help cover medical expenses, travel for care, home support, and financial needs for families.

Living with a biphasic mesothelioma diagnosis

A diagnosis of biphasic mesothelioma can be emotionally and physically overwhelming. Patients often face uncertainty due to the variability in disease behaviour and outcomes. Emotional responses such as anxiety, fear, and frustration are common and understandable.

Support from healthcare teams, family, and support services can help patients manage symptoms and maintain quality of life. Open communication with medical providers allows for informed decision making and better symptom control.

Moving forward after diagnosis

Biphasic mesothelioma is a complex and serious disease, but understanding its characteristics provides clarity during a difficult time. While outcomes are more variable than with other mesothelioma subtypes, appropriate medical care and supportive planning can make a meaningful difference.

Accurate diagnosis, timely treatment, and comprehensive documentation all play a role in managing biphasic mesothelioma. With informed guidance and realistic expectations, patients and families can focus on care, comfort, and making decisions aligned with their priorities.