Key Takeaways
- Mesothelioma is classified by both location (pleural, peritoneal, pericardial, testicular) and cell type (epithelioid, sarcomatoid, biphasic). Cell type directly affects diagnosis, treatment, and prognosis — yet its importance is often overlooked.
- Epithelioid mesothelioma (50%+ of cases) is more responsive to treatment, easier to identify, and less likely to metastasize — making it the most treatable subtype.
- Sarcomatoid mesothelioma (10–20% of cases) is less responsive to treatment, more irregular in growth pattern, and more likely to spread — often leading doctors to recommend palliative care over aggressive treatment.
- Biphasic mesothelioma contains both cell types. Outcomes depend on which type dominates — more epithelioid cells generally means a better prognosis.
- Research tends to treat mesothelioma as a single disease, but the significant differences between cell types suggest they may be better understood as related but distinct cancers requiring different diagnostic and treatment approaches.
What are the Different Types of Mesothelioma?
Mesothelioma is characterized both by its location and cell type. Usually, both of these qualifiers guide the ways in which doctors go about both diagnosis and treatment. For simplicity’s sake, we’ll only be discussing cell type—not location (like pleural, peritoneal, etc. You can learn more about that here). There are three histological types of mesothelioma cells:
- Epithelioid. This is the most common type of mesothelioma, with over half of all patients presenting with this type. It has a uniform cell shape, organelles, and tends to remain connected.
- Sarcomatoid. This is the second most common type of mesothelioma, accounting for about 10-20% of all cases. This type of cell is irregular in shape and presentation, and has a markedly different growth pattern compared to epithelioid.
- Biphasic. This is a combination of epithelioid and sarcomatoid, in which a patient presents with at least 10% of each cell type. Depending on the amount of each cell type present, patients may experience symptoms that more closely align to one cell type over another.
In order to diagnose mesothelioma, patients usually receive a biopsy, or a removal of a sample of living tissue. During biopsy analysis, some clinicians opt to look at the histology—or cell type makeup—of the sample.
Do Different Cell Types Mean Different Diagnostic and Treatment Models?
Different cell types have different characteristics during all points of mesothelioma development.
Epithelioid mesothelioma:
- Is relatively more responsive to treatment
- Is more easily identifiable (meaning it’s more consistent in presentation)
- Has the tendency to stay “clumped together,” meaning there’s a lower chance of metastasis (or growth beyond the initial cancerous site)
Sarcomatoid mesothelioma:
- Is less responsive to treatment (more aggressive)
- Has less uniform shapes, presentation, and growth patterns
- Is more likely to metastasize
So, even though they’re both categorized as mesothelioma, epithelioid and sarcomatoid cell types require different a.) diagnostic models; and b.) plans for treatment. For instance, some doctors will recommend a more rigorous treatment approach for patients with epithelioid mesothelioma, as it’s known that cell type is more responsive to treatment. For sarcomatoid (or sarcomatoid-dominant biphasic), doctors might opt for palliative care or hospice rather than a regimen of chemotherapy or surgery.
Importantly, the cell type of mesothelioma contributes to treatment models and projected outcomes (prognosis). While establishing cell type is a critical part of the diagnostic process, its importance is often overlooked. Using cell type to guide both diagnosis and treatment trajectories should be paramount.
Instead of focusing research efforts on how to treat sarcomatoid mesothelioma or investigating how one cell type develops over another, research conceptualizes mesothelioma as a monolith. Ideally, this will change: as we learn more about sarcomatoid mesothelioma—how it forms, how to intercept its development, how to better manage its irregularity—we might think about mesothelioma in different, less rigid ways. By acknowledging the importance of cell types, there’s room for the scientific imagination to investigate the different types of mesothelioma as “different” cancers.
If you or a loved one has been diagnosed with mesothelioma, please call us at (800) 505-6000. We are here to help. You can also fill out our simple contact form for more information.
Frequently Asked Questions
Why does cell type matter for mesothelioma treatment?
Cell type matters because each subtype behaves differently and responds differently to treatment. Epithelioid mesothelioma tends to stay clumped together (lower metastasis risk) and is more responsive to chemotherapy and surgery. Sarcomatoid mesothelioma is more aggressive, more likely to spread, and less responsive to treatment — often leading doctors to recommend palliative care instead of aggressive intervention. Without identifying the cell type, doctors cannot develop the most appropriate treatment plan.
How is the cell type determined?
Cell type is determined through a biopsy — a procedure that removes a sample of living tissue from the tumor site. During laboratory analysis, pathologists examine the histology (cell type makeup) of the sample to classify it as epithelioid, sarcomatoid, or biphasic. This step is critical for treatment planning but is sometimes overlooked in favor of broader diagnostic assessments.
How does epithelioid mesothelioma differ from sarcomatoid?
The key differences:
- Epithelioid — uniform cell shape, tends to stay connected in clusters, more responsive to treatment, easier to identify, lower chance of metastasis
- Sarcomatoid — irregular shape and growth pattern, less responsive to treatment, more likely to metastasize, harder to identify and often misdiagnosed as other cancers
These differences are significant enough that some researchers argue they should be treated as distinct cancers rather than subtypes of the same disease.
Should mesothelioma cell types be treated as different cancers?
Some researchers believe yes. Current mesothelioma research tends to conceptualize the disease as a single entity, but the significant behavioral differences between epithelioid and sarcomatoid cells suggest they may warrant separate diagnostic models, treatment protocols, and research pathways. By treating sarcomatoid mesothelioma as a distinct problem — investigating how it forms, how to intercept its development, and how to manage its irregularity — scientists may develop more effective, targeted approaches rather than applying one-size-fits-all treatments.
What should I do if I’ve been diagnosed with mesothelioma?
If you or a loved one has been diagnosed with mesothelioma, ask your oncologist about your cell type — it directly affects your treatment options and prognosis. Understanding whether your mesothelioma is epithelioid, sarcomatoid, or biphasic is a critical piece of information for developing the best possible treatment plan. For information about your legal options, call (800) 505-6000 or fill out our contact form for a free consultation.
