Written By: Devin Golden
Malignant Epithelioid Mesothelioma
Epithelioid mesothelioma cancer is the most common mesothelioma cell type, accounting for more than half of cases. Patients with this diagnosis typically have the most promising prognosis, as this cell type is the most treatable.
Medically Reviewed By
Dr. Stephen Williams
Precision Oncology Scientist
Medically Reviewed By
Dr. Stephen Williams
Precision Oncology Scientist
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Important Facts About Epithelioid Mesothelioma
- Epithelioid mesothelioma is a commonly diagnosed cell type for this cancer, as it is present in 70% of cases.
- There are many mesothelioma treatment options available for patients with epithelioid mesothelioma.
- Patients with this cell type typically have promising survival rates, especially following successful mesothelioma surgery.
What Is Malignant Epithelioid Mesothelioma?
Epithelioid mesothelioma is the most common cell type of malignant mesothelioma, accounting for approximately 60-70% of cases. Mesothelioma is a rare and aggressive cancer that develops in the thin layer of tissue (the mesothelium) covering many internal organs, typically caused by exposure to asbestos.
Currently, there are many mesothelioma treatment options available for patients with epithelioid mesothelioma. Patients with epithelioid mesothelioma have a better prognosis compared to the other two cell types: sarcomatoid and biphasic.
Mesothelial cells genetically mutate due to irritation caused by exposure to asbestos, which is the primary cause of mesothelioma. Once asbestos fibers enter the body, the toxic particles can become lodged in the mesothelium, which is the lining of the lungs, abdomen, and heart.
The mesothelium is made up of healthy epithelial cells, which means irritation of the mesothelium impacts the epithelial cells. Diseased epithelial cells of the mesothelium can turn into mesothelioma tumors.
Epithelioid Cell Type
Patients with this cell type of mesothelioma often have a better prognosis and more treatment options than people with sarcomatoid mesothelioma or biphasic mesothelioma. Epithelioid cells are easy to identify and remove during surgery. They also metastasize (spread) slower.
Characteristics of Epithelioid Mesothelioma Cells
Cell Prevalence
The epithelioid mesothelioma cell type accounts for between 60% and 70% of mesothelioma cases.
Cell Description
Epithelioid cells have a clearly defined, elongated egg-shape structure. They often clump together and have a pink cytoplasm. The cells’ visible nuclei make them easier to differentiate from healthy cells or sarcomatoid mesothelioma cells.
Cell Behavior
Epithelioid cells divide at a much faster rate than other cell types, contributing to faster tumor growth. However, these cells maintain their cell-to-cell adhesive properties, which reduces the rate of metastasis and makes them easier to remove during surgery.
What Causes Epithelioid Mesothelioma?
The human body is made up of four types of cells: epithelial cells, nerve cells, muscle cells, and connective tissue cells. Epithelial cells are those cells found in the linings of the lungs, abdomen, and heart. The lining of these organs is called the mesothelium.
Epithelioid mesothelioma cells originate when healthy epithelial cells are irritated, such as during asbestos exposure, ultimately leading to DNA damage in healthy cells. Inhalation of these fibrous minerals causes chronic inflammation, leading to genetic mutations in the mesothelial cells lining the mesothelium, promoting abnormal growth.
Mesothelial cells make up the thin linings around the lungs, inside the chest wall and the abdominal cavity, called the mesothelium.
Asbestos fibers can remain in the body for more than a decade, causing inflammation and cell damage. Genetic changes can occur in the mesothelial cells resulting in the development of the rare cancer, mesothelioma.
Epithelioid mesothelioma is the most common type of mesothelioma. The epithelioid mesothelioma cells often form multiple nodules within the mesothelium lining.
Epithelioid Mesothelioma Diagnosis
To diagnose epithelioid mesothelioma, doctors perform a biopsy to collect tissue from the affected area. For epithelioid pleural mesothelioma, this means taking a sample from the lung lining. For peritoneal mesothelioma, the sample is taken from the patient’s abdominal lining.
After the biopsy, the tissue undergoes histology, where it is examined under a microscope to detect cancer cells. If cancer is confirmed, the results are detailed in a pathology report, which identifies the specific cell types present, helping to guide treatment options.
Epithelioid Mesothelioma Diagnosis
A pathologist will use a process called immunohistochemistry to confirm the patient’s mesothelioma diagnosis. Immunohistochemistry is a process to identify antigens in cells.
The immunohistochemical markers include:
| Calretinin | Demonstrated in nearly all cases |
|---|---|
| Cytokeratin 5 or 5/6 | Expressed in between 75% and 100% of cases |
| Wilms’ tumor-I antigen (WT1) | Shown in between 70% and 95% of cases |
| Podoplanin (D2-40) | Demonstrated in between 90% and 100% of cases |
Epithelioid Mesothelioma Symptoms
Symptoms can vary from patient to patient and depending on the site of the tumor such as in the lungs or the abdomen.
Symptoms of epithelioid pleural mesothelioma include:
- Shortness of breath
- Chest or lower back pain
- Coughing
- Difficulty swallowing
- Arm or face swelling
- Pleural effusions
Symptoms of epithelioid peritoneal mesothelioma include:
- Abdominal pain
- Nausea
- Vomiting
- Constipation
- Bowel issues
- Ascites (fluid in the abdomen)
Connect with
a Peritoneal Mesothelioma Specialist
Epithelioid Mesothelioma Treatment Options
As for most cancer types, treatment options for epithelioid mesothelioma will depend on the cancer’s stage and location, and the patient’s overall health. Epithelioid mesothelioma generally responds better to treatment than other mesothelioma cell types, offering more potential for management and improved overall survival rate (OS). The standard of care is surgery, chemotherapy, radiation therapy and immunotherapy.
Epithelioid Mesothelioma Surgery
There are three primary surgical options for malignant mesothelioma.
Patients with epithelioid pleural mesothelioma have two surgical options: extrapleural pneumonectomy and pleurectomy with decortication.
Extrapleural pneumonectomy (EPP) involves the removal of the affected lung, the pleura, potentially the pericardium (sac around the heart) and part of the diaphragm.
A study published in the Annals of Thoracic Surgery showed the effectiveness of EPP surgery for cases of epithelioid mesothelioma. The average survival time was 20.6 months.
Pleurectomy with decortication (P/D) does not remove the lung but does remove the pleura and possibly the pericardium and diaphragm. P/D is attributed to better quality of life for patients since neither lung is removed.
Epithelioid peritoneal mesothelioma patients only have one surgical option: cytoreduction with hyperthermic intraperitoneal chemotherapy (HIPEC). This two-part procedure begins with cytoreduction (debulking), which removes as many mesothelioma tumors as possible by resecting the peritoneum and, if needed, part of the intestines or other affected abdominal organs. The second part of the surgery is administering heated intraperitoneal chemotherapy directly into the abdomen.
Chemotherapy, Immunotherapy, Radiation and Emerging Epithelioid Mesothelioma Treatment Methods
Mesothelioma specialists use other methods to treat patients diagnosed with mesothelioma. Chemotherapy, immunotherapy and radiation are the standard forms.
Mesothelioma chemotherapy is a common treatment method. Pemetrexed and cisplatin are the chemotherapy drugs approved by the FDA for mesothelioma treatment. Chemotherapy drugs act by damaging and inhibiting DNA or RNA synthesis, leading to rapid cell death.
Mesothelioma immunotherapy is an emerging option for treatment.
Nivolumab (Opdivo), ipilimumab (Yervoy) and pembrolizumab (Keytruda) are FDA-approved immunotherapy drugs for epithelioid pleural mesothelioma, but doctors support the use of immunotherapy for other types of mesothelioma. Immunotherapy drugs help activate our immune system by recognizing and attacking cancer cells, leading to reduced tumor burden.
Radiation is often used as a second-line treatment for epithelioid pleural mesothelioma. It is not used for other types of mesothelioma due to the increased risk of damaging nearby vital organs. Radiation beams can damage the organs and lead to further health issues.
The Orphanet Journal of Rare Diseases published a report that radiation therapy combined with EPP increases epithelioid patients’ median survival to 33 months (nearly three years).
There have also been some successes in clinical trials with alternative treatment options, such as combination therapy, gene therapy, photodynamic therapy and oncolytic viruses.
Subtypes of Epithelioid Mesothelioma
Within epithelioid mesothelioma, there are several subtypes classified by pathologists that vary in characteristics, distribution and progression. While many pathologists recognize overlaps of some subtypes, their distinctions are clinically significant for the treatment strategy recommended.
The five subtypes of epithelioid mesothelioma are:
- Adenoid
- Small cell
- Cystic
- Papillary
- Deciduoid
Epithelioid Mesothelioma Prognosis
The prognosis for patients diagnosed with the epithelioid mesothelioma cell type is generally better compared to patients with sarcomatoid or biphasic mesothelioma. Most studies report that the prognosis can range from ~10-20 months depending on various factors, including stage of disease, patient health and access to care. According to the Orphanet Journal of Rare Diseases, most patients who survive for two years after their diagnosis have this specific mesothelioma cell type.
Patients can have varying life expectancies. Epithelioid pleural mesothelioma is most commonly diagnosed. However, epithelioid peritoneal mesothelioma usually has a more promising prognosis.
A mesothelioma prognosis is determined by many factors, but the main factor to consider is whether the patient has been diagnosed with pleural or peritoneal:
According to a study published on UpToDate, epithelioid pleural mesothelioma patients survived for an average of 19 months.
Epithelioid peritoneal mesothelioma patients survived for an average of 55 months.
Other factors, like age, stage of mesothelioma and overall health, can impact a patient’s life expectancy.
There are many ways patients can improve their survival. One way is seeing a specialist or opting for new treatments. Connect with one of our patient advocates, registered nurse Karen Ritter, at karen@mesotheliomaguide.com for help finding a mesothelioma specialist or clinical trial.
Frequently Asked Questions About Epithelioid Mesothelioma
What does epithelioid mesothelioma look like?
Epithelioid cells have a clear egg shape. They have a visible pink cytoplasm (the cell area surrounding the nucleus) and clump together with defined borders. These cells also have visible, dark-colored nuclei.
How common is epithelioid mesothelioma?
Epithelioid mesothelioma occurs in at least 50% of all cases of this cancer. There are around 3,000 diagnosed mesothelioma cases in the United States each year, which means there are at least 1,500 epithelioid cases.
What is the survival time for epithelioid mesothelioma?
Patients diagnosed with epithelioid mesothelioma have the best prognosis of the three cell-type variations. Pleural mesothelioma patients live for an average of 19 months after diagnosis. Peritoneal mesothelioma patients survive for an average of 55 months.
How is epithelioid mesothelioma treated?
Doctors treat patients with epithelioid mesothelioma using a combination of therapies (i.e. chemotherapy, surgery, immunotherapy or radiation) based on the patient’s overall health, disease stage, and location of the cancer. Treatment strategy aims to prolong survival, manage symptoms, and improve quality of life.
Sources & Author
- About Malignant Mesothelioma. American Cancer Society. Retrieved from: https://www.cancer.org/content/dam/CRC/PDF/Public/8733.00.pdf. Accessed: 10/01/19.
- Epithelioid Cell. ScienceDirect. Retrieved from: https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/epithelioid-cell. Accessed: 10/04/19.
- Mesothelioma versus adenocarcinoma. Pathology Outlines. Retrieved from: http://www.pathologyoutlines.com/topic/pleuramesovsadeno.html. Accessed: 04/17/19.
- Signs and Symptoms of Mesothelioma. American Cancer Society. Retrieved from: https://www.cancer.org/cancer/malignant-mesothelioma/detection-diagnosis-staging/signs-symptoms.html. Accessed: 10/04/19.
- Immunohistochemistry. National Cancer Institute. Retrieved from: https://www.cancer.gov/publications/dictionaries/cancer-terms/def/immunohistochemistry. Accessed: 10/04/19.
- Guidelines for Pathologic Diagnosis of Malignant Mesothelioma. International Mesothelioma Interest Group. Retrieved from: https://www.archivesofpathology.org/doi/pdf/10.5858/arpa.2017-0124-RA. Accessed: 10/04/19.
- Long-term survival outcomes of cytoreductive surgery and perioperative intraperitoneal chemotherapy: Single-institutional experience with 1225 cases. Journal of Surgical Oncology. Retrieved from: https://www.ncbi.nlm.nih.gov/pubmed/31309588. Accessed: 07/29/19.
- Malignant mesothelioma. Orphanet Journal of Rare Diseases. Retrieved from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2652430/. Accessed: 10/04/19.
- Malignant Pleural Mesothelioma. Edited by Kenneth O’Byrne and Valerie Rusch. Oxford University Press. 2006.
