Epithelioid Mesothelioma

What Is Epithelial Mesothelioma?

Epithelial mesothelioma cancer, also known as epithelioid mesothelioma, is the most common of the disease’s three cell types. Asbestos exposure is the primary cause of epithelioid mesothelioma.

Epithelial mesothelioma accounts for 50% to 70% of the 3,000 mesothelioma cases diagnosed each year. That means doctors diagnose between 1,500 to 2,100 epithelioid mesothelioma patients annually. The types of mesothelioma develop in the lining of the lungs (pleural), abdomen (peritoneal), heart (pericardial) or testes (testicular). 

Epithelioid mesothelioma has the best prognosis because it is the most responsive to aggressive treatment. Patients with this tumor cell type live about six months longer than those with biphasic or sarcomatoid cell types.

“The epithelial type does tend to be more favorable,” mesothelioma specialist Dr. Andrea Wolf of Mount Sinai Hospital told The Mesothelioma Center at Asbestos.com. “It does tend to respond to chemotherapy a little more easily.”

Epithelioid cells make up approximately 75% of peritoneal mesothelioma tumors. A study of 144 pleural mesothelioma patients published in The Annals of Thoracic Surgery reported 53.5% had pure epithelioid tumors.

What Causes Epithelioid Mesothelioma?

The primary risk factor and cause of epithelioid mesothelioma is the same as other cell types of mesothelioma: exposure to asbestos. Inhalation or ingestion of asbestos fibers causes inflammation and DNA damage that leads to cancer development decades later.

Most people diagnosed with epithelioid mesothelioma worked with asbestos products long before their diagnosis. There’s a latency period of 20 to 60 years associated with the epithelioid type and all other cell types of mesothelioma.

What Are the Symptoms of Epithelioid Mesothelioma?

Mesothelioma symptoms are the same, no matter the cell type. A person with the epithelial form will have similar symptoms as the sarcomatoid type. However, the cell type affects which treatments are most helpful.

Talk to your doctor if you experience any of these symptoms. Be as specific as possible so they can order the correct diagnostic tests for you.

How Is Epithelioid Mesothelioma Diagnosed?

Diagnosing epithelioid mesothelioma requires several tests, including imaging scans, biopsies and blood tests.

Imaging scans can show lung abnormalities, but they cannot diagnose cancer. A tissue biopsy is the only way to diagnose epithelial mesothelioma. This procedure samples the lung tissue to confirm the cell type under a microscope.

Epithelial mesothelioma cells clump together in groups and do not tend to travel. These cells are less likely to spread to other areas of the body. This improves the prognosis of the epithelial type compared to sarcomatoid mesothelioma.

The cells of epithelial malignant mesothelioma can take on a variety of shapes and sizes. These include cuboid (square), columnar (long) or squamous (flat). They are also characterized by a visible nucleus that contains DNA.

Receiving a cancer diagnosis can be an emotionally and physically difficult time for patients and their loved ones. Multiple rounds of tests, unfamiliar terms and procedures can be overwhelming. Your mesothelioma specialist will guide you through your journey.

Understanding Your Pathology Report

The pathology report is the outcome of the diagnostic process. This report provides the definitive diagnosis and describes the types of mesothelioma cells found in a patient’s tumors.  

There are only a small number of mesothelioma pathologists in practice. These specialists use microscopes to view cells up close. Immunohistochemistry is a lab test that helps pathologists classify cancer cell types. They prepare samples of tissue with chemical stains to reveal immunohistochemical markers of epithelioid cells, including calretinin, cytokeratin 5 and 6, WT-1 protein and podoplanin. The stains make the cells’ features stand out.

After a biopsy, the pathologist will create a report for your physician. This report includes cell distribution and a final diagnosis. The cell type informs your doctor how your cancer might progress. It also determines which treatment options may be best.

When you review the pathology report with your doctor, ask them to explain your cell type, cancer stage, tumor grade (speed of tumor growth) and how these factors affect your treatment plan and prognosis.

Epithelial Cell Subtypes

Certain epithelioid cell subtypes, such as adenomatoid, are associated with better survival. Information on rare epithelioid cell subtypes is lacking compared to more common subtypes.

Tubulopapillary

This is the most common subtype of epithelioid mesothelioma. This cell type is often well-differentiated, but doctors may mistake it for other cancers. It can appear as adenocarcinoma that has spread to the pleura. It is not the same as well-differentiated papillary mesothelioma tumors, which is a benign form of the disease.

Glandular

Glandular tumors often develop in the pleural lining. They have a pattern made of gland-like (acinar) structures. These cells can appear similar to adenocarcinoma that has spread to the pleura.

Adenomatoid

Adenomatoid mesothelioma is also known as the microglandular cell type. It accounts for 6% of pleural mesothelioma cases. Pleural, peritoneal or pericardial mesotheliomas may all feature an adenomatoid differentiation. These cells can occur in benign and malignant tissue. In the peritoneum they behave as benign lesions and respond well to treatment. Adenomatoid cells found in the pleura could be benign or malignant.

Small Cell

Small cell mesothelioma grows in a pattern that resembles small cell carcinoma. The tumors do not display the stream, ribbon or rosette patterns in the subtype of lung carcinoma. Many mesothelioma tumors with small cell features are biphasic, which means the tumors contain a combination of epithelial and sarcomatoid cells. This cell type has a survival of about eight months.

Solid

There are two patterns within the solid subtype. Solid, well-differentiated epithelial type is more common. This pattern consists of round cells in nests, cords or sheets. Poorly differentiated cells appear unorganized with straight sides. Pathologists may mistake well-differentiated cells for benign reactive mesothelial hyperplasia. The poorly differentiated pattern looks like large cell carcinoma or lymphoma.

Deciduoid

Deciduoid mesothelioma is a rare epithelial subtype. Doctors have diagnosed fewer than 50 cases. Less than half of all deciduoid mesothelioma cases are pleural, forming in the lining of the lungs. A roughly equal number of deciduoid cases occur in the peritoneum. This type features large cells that are either round or have sharp borders. It can be mistaken for several other types of cancer, including squamous cell carcinoma, a type of lung cancer.

What Is the Survival Rate of Epithelial Mesothelioma?

An epithelial prognosis includes cancer survival rates and life expectancy. The life expectancy of epithelial malignant mesothelioma patients is 18 months. The five-year survival rate is 12% for epithelioid pleural mesothelioma. Epithelioid patients also live an average of 200 days longer than patients with other cell types.

The journal Pathology published a study of peritoneal mesothelioma showing a median survival of 55 months for patients with epithelioid cells compared to 13 months for patients with biphasic cells. 

The biphasic cell type consists of a mixture of epithelial and sarcomatoid cells. Patients with this type have a median survival of about 10 months. Those with the sarcomatoid type have a median survival of seven months. The overall survival of all cell types drops when the disease metastasizes or spreads. 

But, despite the spread of cancer, a mesothelioma specialist can still tailor a treatment at this stage of your disease. There are clinical trials and other options for patients with a more metastasized cancer.

How Is Epithelioid Mesothelioma Treated?

Epithelioid mesothelioma treatment will depend on the cancer stage, extent of tumors and overall health of the patient. The goals of treatment are to extend survival, manage symptoms and improve quality of life. Of the three types, malignant epithelial pleural mesothelioma responds best to treatment.

Doctors treat early-stage epithelioid mesothelioma aggressively with a combination of surgery, chemotherapy and radiation therapy. According to a 2019 report in The Annals of Thoracic Surgery, combination therapy resulted in significantly better outcomes for patients with epithelial malignant pleural mesothelioma.

As cancer progresses, it has a higher chance of spreading and metastasizing to other areas, making surgery less beneficial. Late-stage cases respond better to palliative care with immunotherapy, chemotherapy and Tumor Treating Fields therapy.

Surgery

Surgery is a mainstay of early-stage epithelial mesothelioma treatment. Surgeries for pleural mesothelioma help patients live an average of two years. HIPEC surgery helps peritoneal patients live at least five years.

Surgery offers the greatest survival benefit, but it also presents the greatest risk of complications, including infection and kidney failure.

Chemotherapy

The standard, U.S. Food and Drug Administration-approved chemotherapy for treating epithelioid mesothelioma is a combination of Alimta (pemetrexed) and cisplatin or carboplatin. It helps patients at all stages live at least one year. The combination of chemotherapy and Tumor Treating Fields therapy has an overall survival around 18 months.

Potential side effects of chemotherapy include nausea, vomiting, weight loss and fever.

Radiation Therapy

Radiation therapy may be used alone at all stages or in combination with surgery and chemotherapy at early stages. Radiation is not curative for mesothelioma, but it can help manage symptoms, lessen pain and prevent local recurrence.

Possible side effects of radiation include fatigue, skin problems, shortness of breath, cough and scarring of the lungs.

Immunotherapy

In October 2020, the FDA approved the combination of immunotherapy drugs Opdivo (nivolumab) and Yervoy (ipilimumab) as a first-line treatment for inoperable pleural mesothelioma. This combination has a median survival of 18 months.

Side effects of immunotherapy may include fever, body aches, fatigue, diarrhea and loss of appetite.

A mesothelioma specialist at a top cancer center has the experience to diagnose and treat epithelioid mesothelioma effectively. The specialists at top cancer centers offer clinical trials and multidisciplinary treatment to control the disease with different therapies.

Common Questions About Epithelioid Mesothelioma

Where can I get treatment for epithelial cell mesothelioma?

Most oncologists are not trained to treat epithelioid mesothelioma. Look for mesothelioma specialists who have trained for years in the treatment of pleural and peritoneal mesothelioma. Our Patient Advocates can help you find a top doctor who treats epithelial mesothelioma.

Can epithelioid mesothelioma be prevented?

Avoiding the primary cause of mesothelioma – asbestos exposure – is the best way to prevent the disease. If you have a history of asbestos exposure, talk to your doctor about cancer screenings, which may aid in an early diagnosis.

Is epithelioid mesothelioma curable?

Unfortunately, epithelioid mesothelioma has no cure. But patients with the epithelioid cell type have the most mesothelioma treatment options. This cell type responds the best to all forms of treatment.

Is there any ongoing research on epithelioid mesothelioma?

Yes, clinical trials are constantly looking for mesothelioma patients with the epithelioid cell type. Clinical trials look for these participants because epithelioid is the most common cell type of the disease. Studying epithelioid patients lets researchers know how a drug or therapy will affect the majority of patients diagnosed with mesothelioma.

How can epithelial cells turn into mesothelioma?

Epithelial cells line the airways and are constantly exposed to substances from the air you breathe. One of the main causes of mesothelioma is asbestos exposure. When you inhale asbestos fibers, they can become trapped in the lungs and induce inflammation. Long-term inflammation can lead to mutations in epithelial cells, eventually giving rise to cancer.