Epithelioid Mesothelioma
What Is Epithelioid Mesothelioma?
Malignant mesothelioma is categorized into different histological subtypes based on the appearance and behavior of the cancer cells under a microscope. These subtypes help doctors understand how the disease is likely to progress and which treatments may work best. Learn more about histology and its relation to cancer.
Epithelioid mesothelioma is the most common of these subtypes. It is characterized by relatively uniform, cube-shaped or columnar cells that form organized structures like tubules, papillae, or solid sheets. These cells resemble healthy epithelial cells, which line many of the body's organs and cavities.
Where Is Epithelioid Mesothelioma Found?
Epithelioid mesothelioma can develop in any of the serosal linings of the body, but it is most frequently found in the pleura, the thin membrane surrounding the lungs. It can also occur in the peritoneum (the lining of the abdominal cavity), and less commonly in the pericardium (the lining around the heart) or the tunica vaginalis (the lining of the testes). The pleural location accounts for the majority of cases, as the pleura is the most common site for asbestos fibers to become lodged after inhalation.
How Does Epithelioid Mesothelioma Behave Compared to Other Cell Types?
Epithelioid mesothelioma is generally considered the least aggressive and most treatable of the three main mesothelioma cell types (epithelioid, sarcomatoid, and biphasic). It tends to grow and spread more slowly than the sarcomatoid subtype, which is highly aggressive and resistant to treatment. Additionally, epithelioid mesothelioma is more likely to respond to therapies such as surgery, chemotherapy, and radiation. This improved responsiveness is attributed to the organized structure of the cells, which makes them easier to target with treatment.
Patients with epithelioid mesothelioma typically have a better prognosis compared to those with sarcomatoid or biphasic mesothelioma. Studies suggest that the median survival for patients with this subtype is longer, often ranging from 12 to 24 months, depending on the stage of the disease and the treatment approach.
What Percentage of Cases Does Epithelioid Mesothelioma Represent?
Epithelioid mesothelioma is the most prevalent subtype, accounting for approximately 55% to 65% of all mesothelioma cases. This high prevalence makes it the most studied and best understood of the mesothelioma subtypes. The remaining cases are divided between the sarcomatoid subtype (10% to 15%) and the biphasic subtype (20% to 35%), which contains a mix of both epithelioid and sarcomatoid cells.
Additional Pertinent Information
The diagnosis of epithelioid mesothelioma often requires advanced techniques, as its cells can resemble those of other cancers, such as adenocarcinoma. Pathologists use immunohistochemical staining and other diagnostic tools to differentiate epithelioid mesothelioma from other malignancies. Early and accurate diagnosis is critical, as it allows patients to access treatment options that can improve quality of life and extend survival.
In summary, epithelioid mesothelioma is the most common and treatable subtype of mesothelioma, primarily affecting the pleura but also found in other serosal linings. Its relatively slow progression and better response to treatment offer hope for patients diagnosed with this form of asbestos-related cancer.
How Epithelioid Mesothelioma Differs from Other Types
Epithelioid mesothelioma is distinct from the other two main mesothelioma subtypes—sarcomatoid and biphasic—in several key ways, including its cellular structure, growth behavior, treatment responsiveness, and overall prognosis. These differences are critical for diagnosis, treatment planning, and understanding patient outcomes.
Structure of Cells Under a Microscope
Under a microscope, epithelioid mesothelioma cells are relatively uniform in appearance. They are cube-shaped or columnar and often form organized structures such as tubules, papillae, or solid sheets. These cells closely resemble normal epithelial cells, which line organs and tissues in the body. This organized and differentiated structure makes epithelioid mesothelioma easier to identify and distinguish from other cancers, such as adenocarcinoma, using immunohistochemical staining.
In contrast:
Sarcomatoid mesothelioma cells are spindle-shaped, elongated, and less organized. They resemble cells found in connective tissue, making them harder to differentiate from other sarcomas.
Biphasic mesothelioma contains a mix of both epithelioid and sarcomatoid cells, with the proportion of each type varying from case to case. This mixed structure can complicate diagnosis and treatment.
Growth Rate and Pattern
Epithelioid mesothelioma is the least aggressive of the three subtypes. It tends to grow and spread more slowly compared to sarcomatoid mesothelioma, which is highly invasive and spreads rapidly to distant tissues. Epithelioid mesothelioma typically follows a more localized growth pattern, often spreading to nearby lymph nodes before advancing to other areas.
In contrast:
Sarcomatoid mesothelioma is highly aggressive and invasive, often spreading quickly to distant organs and tissues. Its rapid progression makes it more challenging to treat effectively.
Biphasic mesothelioma exhibits a combination of growth behaviors, depending on the proportion of epithelioid and sarcomatoid cells. Cases with a higher percentage of sarcomatoid cells tend to behave more aggressively.
Treatment Responsiveness
Epithelioid mesothelioma is the most responsive to treatment among the three subtypes. Its organized cellular structure and slower growth rate make it more amenable to therapies such as surgery, chemotherapy, and radiation. Patients with epithelioid mesothelioma are often better candidates for aggressive surgical interventions, such as pleurectomy/decortication (P/D) or extrapleural pneumonectomy (EPP), as well as multimodal treatment approaches.
In contrast:
Sarcomatoid mesothelioma is highly resistant to treatment. Its disorganized cellular structure and rapid spread make it less likely to respond to surgery, chemotherapy, or radiation.
Biphasic mesothelioma has variable treatment responsiveness, depending on the ratio of epithelioid to sarcomatoid cells. Cases with a higher proportion of epithelioid cells tend to respond better to treatment.
Prognosis Comparison
Epithelioid mesothelioma is associated with the best prognosis among the three subtypes. Studies show that patients with this subtype have a median survival of 12 to 24 months, depending on factors such as disease stage, patient age, and treatment approach. This is significantly longer than the survival rates for sarcomatoid and biphasic mesothelioma.
In contrast:
Sarcomatoid mesothelioma has the poorest prognosis, with a median survival of only 6 to 12 months. Its aggressive nature and resistance to treatment contribute to this outcome.
Biphasic mesothelioma has an intermediate prognosis, with survival rates depending on the proportion of epithelioid versus sarcomatoid cells. Patients with a higher percentage of epithelioid cells tend to have better outcomes.
Additional Pertinent Information
The differences between these subtypes highlight the importance of accurate diagnosis. Pathologists use advanced techniques, such as immunohistochemical staining and molecular testing, to differentiate between epithelioid, sarcomatoid, and biphasic mesothelioma. This distinction is crucial for determining the most effective treatment plan and providing patients with a realistic understanding of their prognosis.
In summary, epithelioid mesothelioma differs from other types in its organized cellular structure, slower growth rate, better treatment responsiveness, and more favorable prognosis. These characteristics make it the most treatable and survivable form of mesothelioma, offering hope to patients diagnosed with this subtype.
How Doctors Identify the Epithelioid Subtype
Accurately identifying the epithelioid subtype of mesothelioma is critical for determining the best treatment options and providing an accurate prognosis. Diagnosis involves a combination of biopsy, histological examination, and immunohistochemical testing. Expert pathology is essential, as misclassification can lead to inappropriate treatment and poorer outcomes.
Biopsy and Histology (Microscopic Review)
The first step in identifying the epithelioid subtype is obtaining a tissue sample through a biopsy. There are several methods for collecting biopsy samples, including:
Thoracoscopic biopsy: A minimally invasive procedure where a camera and instruments are inserted into the chest to collect tissue.
CT-guided needle biopsy: A needle is guided by imaging to collect tissue from the affected area.
Open surgical biopsy: A more invasive procedure used when other methods fail to provide sufficient tissue.
Once the tissue is collected, it is examined under a microscope by a pathologist. Epithelioid mesothelioma cells are cube-shaped or columnar and tend to form organized structures, such as tubules, papillae, or solid sheets. These cells closely resemble normal epithelial cells, which line organs and tissues. However, their appearance can sometimes overlap with other cancers, such as adenocarcinoma, making further testing necessary.
Immunohistochemical Markers
To confirm the diagnosis and differentiate epithelioid mesothelioma from other cancers, pathologists use immunohistochemical (IHC) staining. This technique involves applying antibodies to the tissue sample to detect specific proteins expressed by mesothelioma cells. Key markers for epithelioid mesothelioma include:
Calretinin: A highly sensitive and specific marker for mesothelioma. It is positive in most cases of epithelioid mesothelioma but negative in adenocarcinoma.
WT-1 (Wilms Tumor-1): A nuclear marker that is strongly expressed in mesothelioma but not in most other cancers, including lung adenocarcinoma.
Cytokeratin 5/6: Another marker commonly expressed in mesothelioma, helping to distinguish it from other malignancies.
D2-40 (podoplanin): A marker that is often positive in mesothelioma and aids in differentiation from other cancers.
Thrombomodulin: Frequently expressed in mesothelioma and used as part of a diagnostic panel.
In contrast, markers such as CEA (carcinoembryonic antigen), MOC-31, and Ber-EP4 are typically negative in mesothelioma but positive in adenocarcinoma. This helps pathologists rule out other cancers that may mimic mesothelioma.
The use of a panel of markers, rather than relying on a single test, is critical for accurate diagnosis. Pathologists often use a combination of positive and negative markers to confirm the epithelioid subtype and exclude other possibilities.
Why Expert Pathology Matters
Diagnosing mesothelioma, particularly the epithelioid subtype, is challenging and requires specialized expertise. Misclassification is a significant concern, as epithelioid mesothelioma can resemble other cancers, such as adenocarcinoma, or even benign conditions. Studies have shown that general pathologists may misdiagnose mesothelioma in a significant number of cases, leading to inappropriate treatment.
Expert pathologists with experience in mesothelioma use advanced techniques, such as IHC staining and molecular testing, to ensure an accurate diagnosis. They are also more likely to recognize subtle differences in cell structure and staining patterns that distinguish mesothelioma from other diseases. In some cases, a second opinion from a mesothelioma specialist is necessary to confirm the diagnosis.
Additional Considerations
Full-thickness biopsy samples: Providing pathologists with full-thickness tissue samples is crucial, as superficial samples may only show reactive changes rather than malignant cells.
Histological subtyping: Identifying the epithelioid subtype is important because it has a better prognosis and responds more favorably to treatment compared to sarcomatoid or biphasic mesothelioma.
Necropsy findings: In rare cases, the diagnosis may only be confirmed post-mortem, as some tumors are difficult to classify during a patient’s lifetime.
Conclusion
The identification of the epithelioid subtype of mesothelioma relies on a combination of biopsy, histological examination, and immunohistochemical testing. Key markers such as calretinin and WT-1 play a vital role in confirming the diagnosis. Expert pathology is essential to avoid misclassification, which can lead to inappropriate treatment and worse outcomes. By ensuring an accurate diagnosis, doctors can provide patients with the most effective treatment options and a clearer understanding of their prognosis.
How The Epithelioid Subtype Affects Treatment Decisions
Which Treatments Typically Work Best
The epithelioid subtype of mesothelioma is generally associated with a better prognosis compared to other subtypes, such as sarcomatoid or biphasic. This subtype tends to respond more favorably to multimodal treatment approaches, which often include a combination of surgery, chemotherapy, and radiation therapy. Studies have shown that patients with epithelioid histology benefit significantly from trimodality therapy, which involves radical surgery (e.g., extrapleural pneumonectomy or pleurectomy/decortication), followed by chemotherapy and radiation therapy. For instance, patients with epithelioid mesothelioma who undergo surgery combined with adjuvant chemotherapy have demonstrated improved survival rates compared to those receiving supportive care alone.
Eligibility for Surgery or HIPEC
Patients with the epithelioid subtype are more likely to be eligible for aggressive surgical interventions, such as extrapleural pneumonectomy or pleurectomy/decortication, due to the less invasive and more localized nature of this subtype. Additionally, for cases involving peritoneal mesothelioma, cytoreductive surgery combined with Hyperthermic Intraperitoneal Chemotherapy (HIPEC) is a viable option. The epithelioid subtype's relatively better prognosis and slower progression make it a suitable candidate for these intensive treatments, provided the patient meets fitness criteria and the disease is at an early stage.
Use of Immunotherapy for Aggressive Types
While the epithelioid subtype generally has a better prognosis, immunotherapy is still being explored as a treatment option, particularly for cases where the disease is more advanced or aggressive. Agents such as immune checkpoint inhibitors (e.g., nivolumab and ipilimumab) have shown promise in clinical trials for mesothelioma, including the epithelioid subtype. However, the response to immunotherapy may vary, and it is often considered as part of a multimodal approach or for patients who are not candidates for surgery.
Notes About Subtype-Specific Clinical Trials
Clinical trials focusing on the epithelioid subtype have provided valuable insights into treatment strategies. For example:
Trials have demonstrated that patients with epithelioid histology benefit more from multimodal therapies compared to those with sarcomatoid or biphasic subtypes.
Research into gene therapy and immunotherapy is ongoing, with some studies exploring the use of these treatments as neoadjuvant (pre-surgery) or adjuvant (post-surgery) options to improve outcomes.
Subtype-specific trials have also highlighted the importance of early diagnosis and tailored treatment plans, emphasizing the need for further research to optimize therapy timing and combinations.
In summary, the epithelioid subtype of mesothelioma significantly influences treatment decisions, with a preference for multimodal approaches, eligibility for aggressive surgical options like HIPEC, and ongoing exploration of immunotherapy and clinical trials to refine and improve outcomes.
Prognosis for Epithelioid Mesothelioma
Median Survival Time
The epithelioid subtype of mesothelioma is associated with the longest median survival time compared to other subtypes, such as sarcomatoid or biphasic. Studies indicate that the median survival for patients with epithelioid mesothelioma ranges from 12 to 30 months, depending on factors such as stage at diagnosis, treatment approach, and overall health. In contrast, the median survival for sarcomatoid and biphasic subtypes is significantly shorter, often between 7 and 12 months.
How Prognosis Changes with Stage/Anatomical Location
The stage of the disease and its anatomical location play a critical role in determining prognosis:
Early-Stage Disease (Stage I or II): Patients diagnosed at an early stage, where the disease is localized, have a significantly better prognosis. Median survival can exceed 24 months, especially with aggressive multimodal treatment.
Advanced-Stage Disease (Stage III or IV): Prognosis worsens as the disease progresses. For late-stage epithelioid mesothelioma, median survival typically falls to 8–12 months due to the spread of the disease to distant organs or lymph nodes.
Anatomical Location: Pleural mesothelioma (affecting the lining of the lungs) is the most common and has a slightly better prognosis for the epithelioid subtype compared to peritoneal mesothelioma (affecting the abdominal lining). However, patients with peritoneal mesothelioma who undergo cytoreductive surgery and HIPEC can achieve extended survival, often exceeding 5 years in some cases.
Factors That Influence Outcomes
Several factors influence the prognosis for patients with epithelioid mesothelioma:
Treatment Center: Outcomes are often better at specialized mesothelioma treatment centers with experienced multidisciplinary teams. These centers are more likely to offer advanced surgical techniques, access to clinical trials, and personalized treatment plans.
Overall Health and Performance Status: Patients with good overall health and a high performance status (e.g., ECOG 0-1) tend to tolerate aggressive treatments better and have improved survival rates.
Age: Younger patients generally have better outcomes due to their ability to withstand intensive therapies.
Treatment Approach: Multimodal therapy, including surgery, chemotherapy, and radiation, significantly improves survival compared to single-modality treatments or supportive care alone.
Absence of Symptoms: Patients without severe symptoms, such as chest pain or significant weight loss, often have a better prognosis, as these symptoms are typically associated with advanced disease.
Histological Confirmation: Accurate diagnosis of the epithelioid subtype is crucial, as it allows for tailored treatment strategies that maximize survival potential.
In summary, the prognosis for epithelioid mesothelioma is more favorable than other subtypes, with median survival times ranging from 12 to 30 months. Early-stage diagnosis, treatment at specialized centers, and good overall health are key factors that can significantly improve outcomes.
Legal and Compensation Considerations for Epithelioid Mesothelioma
A diagnosis of epithelioid mesothelioma often qualifies individuals for legal compensation—including lawsuits, asbestos trust fund claims, and government benefits—because the disease is almost always caused by asbestos exposure.
Why Epithelioid Subtype Matters in Legal Claims:
Better prognosis gives more time to pursue compensation
More responsive to treatment, which can increase the cost of care (and thus the potential claim value)
Still aggressive and life-altering, especially if diagnosed at an advanced stage
Our firm has helped thousands of clients—many with epithelioid mesothelioma—recover compensation for:
Medical bills
Lost income
Caregiver support
Pain and suffering
Funeral costs (in wrongful death cases)
Learn more about mesothelioma lawsuits and legal options
Or call 833-4-ASBESTOS for a free consultation.
Frequently Asked Questions About Epithelioid Mesothelioma
Q: Does the epithelioid subtype mean I’m more likely to survive mesothelioma?
A: Yes. Among the three main subtypes, epithelioid mesothelioma is associated with the longest survival rates—especially if diagnosed early and treated aggressively.
Q: Does my subtype affect which treatments I can get?
A: Absolutely. Patients with the epithelioid subtype are often eligible for surgery and multimodal therapy because their cancer grows more slowly and responds better to treatment.
Q: Can I file a legal claim if I have epithelioid mesothelioma?
A: Yes. In fact, your better prognosis may give you more time to pursue a lawsuit or trust fund claim, which can help pay for your care and support your family.