Malignant Epithelioid Mesothelioma

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Epithelial mesothelioma, also known as epithelioid, is the most common mesothelioma cell type, accounting for 70% of cases. Epithelial mesothelioma responds best to treatment because it is less aggressive than sarcomatoid mesothelioma and spreads slower than other cell types.

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Patient Advocate Karen Selby explains malignant epithelioid mesothelioma.
Patient Advocate Karen Selby explains malignant epithelioid mesothelioma.

What Is Epithelial Mesothelioma?

Epithelial mesothelioma is the most common of the three types of this cancer. Approximately 70% of cases are epithelial. You also may hear the term “epithelioid” to refer to this asbestos-related cancer. Epithelial and epithelioid are used interchangeably.

What Are the Characteristics of Epithelioid Cells?

Epithelial mesothelioma cells clump together in groups. Each cell is square or cubic in appearance. The nucleus — the area of the cell that contains genetic material — is clearly visible in each cell.

Because epithelioid cells lack mobility and adhere closely together, they are less likely to spread compared with sarcomatoid cells. This is one of the reasons epithelial mesothelioma has the best prognosis of the different mesothelioma cancers.

Epithelial Mesothelioma Diagnosis

Epithelial mesothelioma distribution
Epithelioid mesothelioma accounts for the majority of cases.

Accurately diagnosing epithelioid mesothelioma requires multiple steps. Many patients experience significant delays between onset of symptoms and receiving an accurate diagnosis.

Epithelioid Mesothelioma Diagnostic Challenges

  • Early symptoms, such as cough and fatigue, mimic less serious respiratory conditions, according to a 2019 Expert Review of Respiratory Medicine article.
  • Primary care doctors want to rule out common causes of symptoms before referring a patient for chest scans.
  • Even after referral for X-rays, CT scans or an MRI, these tests take time to schedule.
  • Imaging only reveals abnormalities; it cannot determine the cause of abnormal chest areas.
  • Even after imaging results are available, it takes time to schedule an appointment with a surgeon.
  • It can take several weeks or months to get on a surgery schedule.

All of these things may get in the way of obtaining a tissue sample. And only a tumor biopsy — often obtained with thoroscopy or video-assisted thoracic surgery — leads to accurate identification of epithelial mesothelioma.

One of the most important things you can do to minimize diagnostic delays is to share any history of asbestos exposure with your health care provider.

If your doctor knows you’ve been exposed to asbestos, they are more likely to consider a rare cancer such as mesothelioma or another asbestos-related condition.

Role of Immunohistochemistry in Diagnosis

Immunohistochemistry is a laboratory test to detect proteins on the surface of cells. These proteins help classify cancer cell type.

Pathologists use immunohistochemistry to identify epithelioid mesothelioma and differentiate it from another type of cancer called adenocarcinoma.

According to the 2018 ASCO pleural mesothelioma treatment guidelines, immunohistochemistry is a recommended test for suspected mesothelioma tumors.

This analysis will confirm the absence or presence of mesothelioma cell markers, leading to the most accurate diagnosis possible.

Quick Fact:

Your pathology results will show the specific cell type of your cancer. If you haven’t been told your cell type, be sure to ask your doctor and request a copy of the pathology report for your records.

Symptoms of Epithelioid Mesothelioma

Early symptoms of pleural or peritoneal mesothelioma include cough, shortness of breath and lack of appetite. As the disease progresses, more serious symptoms may surface.

Early and Late Mesothelioma Symptoms

  • Shortness of breath
  • Persistent, nonproductive (dry) cough
  • Hoarseness
  • Coughing up blood
  • Low blood oxygen levels and anemia (low iron)
  • Weight loss
  • Feeling full, even without eating
  • Lack of appetite and nausea
  • Fatigue and weakness

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What Are the Epithelial Mesothelioma Treatment Options?

Of the three mesothelioma types, epithelial responds best to treatment. Patients diagnosed with it tend to have more treatment and clinical trial options.

Treatments for epithelioid mesothelioma include:

  • Surgery: Surgery is a mainstay of epithelial mesothelioma treatment, although some patients may not be eligible for it due to other health conditions.
  • Chemotherapy: The standard, FDA-approved chemotherapy for treating epithelioid mesothelioma is a combination of Alimta (pemetrexed) plus cisplatin or carboplatin.
  • Radiation therapy: Radiation therapy may be used alone or in combination with surgery and chemotherapy. Radiation is not curative for mesothelioma, but it can help manage symptoms and lessen pain.
  • Multimodal: According to The Annals of Thoracic Surgery 2019 paper, multimodal therapy, a combination of two or more therapies, resulted in significantly better outcomes for patients with epithelial malignant pleural mesothelioma.

Finding Optimal Mesothelioma Treatment

There are key steps you can take to find the best mesothelioma treatment to meet your needs. Patients who seek out specialty mesothelioma care and receive all of the treatments for which they are eligible have the best life expectancy.

  • See an Expert. A study published April 2019 in The Annals of Thoracic Surgery, suggests many mesothelioma patients do not receive treatment consistent with national guidelines. This is less likely to happen if you go to a high-volume mesothelioma center where doctors see many patients with this rare disease.
  • Consider Alternative Chemotherapy. If you can’t take the FDA-approved chemotherapy cocktail of Alimta (pemetrexed)and cisplatin, work with your doctor to find another chemotherapy plan to best meet your needs.
  • Improve Quality of Life. Ask if adding radiation therapy to your palliative care plan is a good idea. While this treatment modality won’t cure mesothelioma, it shouldn’t be dismissed out of hand. It can help you feel much better.
Median Survival
Treatment Type Median Survival
No Treatment 10.2 Months
Chemotherapy Alone 15.4 Months
Surgery Plus Chemotherapy 21.1 Months
Multimodal (all three) 21.7 Months

If a patient is eligible for aggressive treatment, a combination of surgery and chemotherapy or surgery, chemotherapy and radiation are likely to provide longer survival.

What Is the Prognosis for Epithelioid Mesothelioma?

In 2018, investigators published a detailed analysis of data contained in the National Mesothelioma Virtual Bank.

Compared with other cell types, patients with epithelial disease had an improved prognosis of around 200 additional days of survival. This improved survival rate can amount to years if the cancer is diagnosed in an early stage.

Median survival of epithelioid patients was 18 months, compared with 10 months for patients with biphasic cell type and 7 months for people with sarcomatoid disease.

Epithelial cell type allows patients to access more aggressive treatment plans and innovative clinical trials, especially when they are being seen at a mesothelioma specialty clinic.

What Are the Characteristics of Epithelioid Cell Subtypes?

Epithelioid mesothelioma has several cell subtypes. The cell subtype generally does not affect treatment choices. However, it can help your doctors tell mesothelioma apart from similar cancers, avoiding misdiagnosis.

Tubulopapillary Cell Sample

Tubulopapillary

This is a common subtype of epithelioid mesothelioma. Most tubulopapillary mesotheliomas contain well-differentiated cells. It is possible for doctors without mesothelioma experience to mistake this for adenocarcinoma that has spread to the pleura.

Adenomatoid Cell Type

Adenomatoid

Adenomatoid mesothelioma, also known as microglandular cell type, accounts for 6% of pleural mesothelioma cases. These tumors are made of flat to cube-like cells and are lined by small gland-like structures.

Adenomatoid is sometimes mixed with other kinds of epithelial cells inside a tumor. Doctors may mistake it for benign adenomatoid tumors or metastatic adenocarcinoma of the pleura.

Solid Cell Variant

Solid

The solid subtype has two patterns: Well differentiated and poorly differentiated.

Solid, well-differentiated epithelial type is one of the most common cell patterns seen in mesothelioma. It has round cells in nests, cords or sheets.

The poorly differentiated pattern has relatively unorganized cells that are polygonal — having straight sides — to round in appearance.

A doctor without expertise in mesothelioma may mistake solid, well-differentiated mesothelioma for benign reactive mesothelial hyperplasia. The poorly-differentiated pattern appears similar to lymphoma and large cell carcinoma.

This is another good reason to seek care from a mesothelioma expert. Doctors who have seen the disease many times are less likely to misdiagnose it as something else.

Glandular Cells

Glandular

Tumors with the glandular pattern are mostly composed of gland-like (acinar) structures. This subtype usually develops in the pleural lining. It may be confused with adenocarcinoma that has spread to the pleura.

Deciduoid Mesothelioma Cell Type

Deciduoid

Deciduoid mesothelioma is a rare epithelial subtype that may be caused by factors other than asbestos exposure. This pattern features large round to polygonal cells with sharp borders.

Deciduoid mesothelioma may be mistaken for squamous cell carcinoma, anaplastic large cell lymphoma, gastrointestinal autonomic nerve tumor, pseudotumoral deciduosis, trophoblastic neoplasia and the oxyphilic variant of ovarian clear cell carcinoma.

Well-Differentiated Mesothelioma Cell

Well-Differentiated Papillary Mesothelioma

This cell type is slow-growing, well differentiated and features small bumps or protrusions lined by a single layer of flat cells.

This very rare mesothelioma cell type usually affects young women and is not related to asbestos exposure.

Kasie Coleman, Peritoneal mesothelioma survivor diagnosed in 2010
Kasie Coleman Peritoneal mesothelioma survivor diagnosed in 2010

“Rebuilding and getting back to ‘normal’ isn’t a race for the swift. It’s for those who can endure the highs and lows. There are small victories and setbacks. But eventually, the battle is won.”

Seek Specialty Care

Regardless of cellular subtype, a mesothelioma specialist can help you obtain an accurate diagnosis and receive the best possible therapies for your disease.

Proper treatment and the help of a mesothelioma doctor have helped many people outlive the average mesothelioma prognosis.

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Registered Nurse and Patient Advocate

Karen Selby joined Asbestos.com in 2009. She is a registered nurse with a background in oncology and thoracic surgery and was the regional director of a tissue bank before becoming a Patient Advocate at The Mesothelioma Center. Karen has assisted surgeons with thoracic surgeries such as lung resections, lung transplants, pneumonectomies, pleurectomies and wedge resections. She is also a member of the Academy of Oncology Nurse & Patient Navigators.

Walter Pacheco, Managing Editor at Asbestos.com
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7 Cited Article Sources

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  4. Rossini, M. et al. (2018, April 3). New Perspectives on Diagnosis and Therapy of Malignant Pleural Mesothelioma.
    Retrieved from: https://www.frontiersin.org/articles/10.3389/fonc.2018.00091/full
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    Retrieved from: http://ascopubs.org/doi/pdf/10.1200/JCO.2017.76.6394
  6. Wagas, A. et al. (2018). Factors influencing malignant mesothelioma survival: a retrospective review of the National Mesothelioma Virtual Bank cohort. :
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Last Modified June 26, 2019

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