Epithelioid Mesothelioma

Epithelioid mesothelioma is a cancer caused by asbestos exposure. It is the most common mesothelioma cancer cell type, comprising about 60% of cases.[1] Epithelioid mesothelioma is the least aggressive type, is easiest to treat, and has the best prognosis.

What Are Epithelial Cells?

The body is made up of different types of cells, including epithelial cells:[2]

• The epithelial types are found throughout the body.
• They make up the tissue lining various parts of the body, including the skin, throat, blood vessels, and organs.
• These cells act as the body’s safety barrier.
• Epithelial cells come in various shapes depending on where they are located in the body, but they are generally flat, cube-shaped, or columnar.
• Epithelial cells are usually packed tightly together.
• Because they are so close together, cancers that develop in epithelial cells spread and metastasize more slowly, making them less aggressive cancers.

What Is Epithelioid Mesothelioma?

When most of the malignant cells are epithelial in origin, doctors diagnose epithelioid mesothelioma. Pleural, peritoneal, pericardial, and testicular mesothelioma may all be epithelial.

Epithelial is one of two cell types seen in mesothelioma. It is the most common, accounting for 50 to 70% of cases. Epithelioid mesothelioma is the least aggressive type of cell and responds best to treatment.

Epithelioid Mesothelioma Sub-Types

Pathologists can identify several sub-types of epithelial mesothelioma cells:[3]

• Small cell. Small cell cancers are made up of small, uniform cells. In mesothelioma, these cells can be easily mistaken for those that make up small cell lung cancer.

• Adenomatoid. These cells are both epithelial and characteristic of cells that arise in the body’s glands. Mesothelioma may be misdiagnosed as a benign adenomatoid tumor.

• Tubulopapillary. This cell sub-type forms a distinct pattern of papillary structures and small tubules and is common in mesothelioma. It may be misdiagnosed as an adenocarcinoma spread to the pleura.

• Deciduoid. This is a rare epithelial subtype shaped like large polygons. Because it is so rare, it is easy to misdiagnose.

• Solid. Solid cell types may be poorly or well-differentiated. Well-differentiated solid cells are round and orderly. In the poorly differentiated type, cells are not uniform. This type may be misdiagnosed as lymphoma or large cell carcinoma.

• Cystic. Cystic mesothelioma is most common in the peritoneum and is often benign.

• Well-differentiated. This type is also most common in peritoneal mesothelioma. It is often benign and occurs mostly in younger women with no known asbestos exposure.

• Glomeruloid. These cells are round or oval-shaped and are not common in mesothelioma. They are not thought to be related to asbestos exposure.

What Causes Epithelioid Mesothelioma?

As with other types of mesothelioma, the epithelial sub-type is caused primarily by asbestos exposure. Anyone who worked around asbestos or in an industry that used asbestos decades ago is at risk for this disease.

Rarely, people without known workplace asbestos exposure develop mesothelioma. Other potential causes or contributing factors may include specific genes, environmental exposure, and secondary exposure.

What Are the Symptoms of Epithelioid Mesothelioma?

How Do Doctors Diagnose Epithelioid Mesothelioma?

If you have symptoms of epithelioid mesothelioma, see your doctor. Notify them of any potential asbestos exposure in your past.

A diagnosis of epithelioid mesothelioma begins with a physical exam. Your doctor may then order imaging scans, including X-rays, CT scans, and MRIs. These help rule out other conditions and identify abnormal areas of tissue that may be cancer. At this point, your doctor will probably refer you to an oncologist.

• If they find unusual areas in an imaging scan, a doctor will then take a biopsy, a sample of tissue from the abnormal area.
• Next, a pathologist examines physical characteristics of the cells under a microscope as well as how the cells are ordered.
• This allows the growth to be identified as mesothelial or lung cancer cells.
• The biopsy can also identify if the cells are epithelial or sarcomatoid. If epithelial cells are found, the pathologist will then determine which sub-type they are.

All types of mesothelioma are difficult to diagnose. The work of the pathologist is essential to identifying cell types. This part of the diagnosis helps doctors determine the best course of treatment. If you’re not comfortable with a diagnosis, seek a second opinion.

There is also an innovative new technique that makes the diagnosis of mesothelioma easier. Immunohistochemistry uses antibodies to detect the antigens specific to types of cancer cells.[4]

Doctors can use several of these antibodies to help diagnose epithelial mesothelioma. The technique is particularly useful in differentiating between epithelial mesothelioma and adenocarcinoma, a common misdiagnosis.

What Are the Stages of Epithelioid Mesothelioma?

Regardless of cell type, a complete mesothelioma diagnosis includes assigning a stage from I to IV:

• Stage I epithelioid mesothelioma is very early and rarely diagnosed. At this stage, tumors remain within the pleural or peritoneal tissue.
• Stage II occurs when there has been some spread of the primary tumor. It has not yet spread to lymph nodes at this point but may have invaded nearby tissues, such as the diaphragm or lungs.
• Stage III epithelioid mesothelioma has spread more throughout the region of the original tumor and may have invaded nearby lymph nodes.
• Stage IV means that the cancer has spread extensively and well into lymph nodes. It usually means the cancer has also metastasized.

The earlier the stage at the time of diagnosis, the easier it is to treat cancer, especially mesothelioma. Patients with the epithelial type have a better chance of getting an early-stage diagnosis. It spreads less readily and aggressively than the other cell types.

How Is Epithelioid Mesothelioma Treated?

Epithelioid mesothelioma is easier to treat than other cell types. As with any type of mesothelioma, the treatment plan depends on individual factors, such as age, health, preferences, cancer stage, and type.

In general, epithelioid mesothelioma is treated with a multimodal approach, utilizing two or three of the most common cancer treatments:

• Chemotherapy: Chemotherapy is used to shrink tumors before surgery or to eliminate remaining cancer cells after surgery.
• Surgery: Surgical procedures make up the bulk of treatments for epithelial mesothelioma, removing as much of the tumors as possible.
• Radiation therapy: A treatment plan may include radiation, most often after surgery to eliminate remaining cells or as a palliative procedure to shrink tumors and reduce symptoms.

Surgery for Epithelioid Mesothelioma

Epithelioid mesothelioma is generally considered a resectable type of mesothelioma. This means surgery can potentially remove the entire visible tumor. Surgery is the standard treatment for most patients with this mesothelioma type.[5]

For pleural epithelioid mesothelioma, an extrapleural pneumonectomy, or EPP, is a possible treatment. EPP is a surgical procedure that removes the lung along with the pleura where the cancer originated. Patients must be in generally good health for this complicated and risky surgery.[5]

A less aggressive surgical strategy is called debulking. Debulking is a procedure where a surgeon removes as much of the tumor as possible. Surgery may also be done to remove the pleura on one side of the chest or part of a lung. These are usually combined with chemotherapy and radiation for best results.

Other Treatments for Epithelioid Mesothelioma

• Targeted therapy is a cancer treatment that uses drugs that target specific oncogenic genes or proteins in the tumor. Dasatinib, for example, a multitargeted Src kinase/PDGFR inhibitor, was shown to have antitumor activity against malignant epithelial mesothelioma patients in phase II clinical trials.[6]

• Immunotherapy is used to treat cancer patients using the body’s immune system. Cancer immunotherapies use antibodies that bind to and inhibit functions of proteins, called checkpoints. The most common targets for immunotherapy are PD-1 or PDL1. PDL1, for example, is a protein that helps keep immune cells from attacking normal cells in the body; however, cancer cells express this protein in high amounts to “trick” the immune system into leaving them alone. The therapy blocks it so the immune system recognizes the cancer cells and attacks them.[7]

There are multiple phase II clinical trials investigating the efficiency of the immunotherapy drug Nivolumab alone or in combination with another drug called ipilimumab for malignant epithelial mesothelioma patients.[8]

The FDA recently approved the combination for pleural mesothelioma. It is the first new systemic therapy approved for mesothelioma in 15 years.[9]

What Is the Survival Time for Epithelioid Mesothelioma?

Because epithelial cells stick to one another, they metastasize less readily than sarcomatoid cells. For this reason, epithelial mesothelioma has the best prognosis compared to other cell types. Epithelial cells will eventually metastasize, but they will do so more slowly.

In one study, patients with sarcomatoid mesothelioma had a median survival time of just thirteen months. For the patients with epithelial mesothelioma, the median survival time was fifty-five months.[10]

Other factors affecting prognosis include age, gender, general health, nutrition, and cancer stage. The earlier the stage, the better the prognosis will be; therefore, getting an early diagnosis is essential. If you have been exposed to asbestos during your career, you should receive regular mesothelioma screenings.

Is Epithelioid Mesothelioma Curable?

No type of mesothelioma is officially considered curable. However, epithelioid mesothelioma responds better to treatment than other cell types. Patients with early-stage epithelioid mesothelioma who opt for aggressive, immediate treatment have the best chances of long-term remission.

Should I Choose Aggressive Treatment for Epithelioid Mesothelioma?

Your medical team will outline your treatment options and advise you on the best course of action. Ultimately, the choice comes down to the patient.

With epithelioid mesothelioma, you are more likely to be eligible for aggressive treatments that increase your life expectancy. On the other hand, these treatments can be uncomfortable, come with risks, and may diminish quality of life.

To make this decision, listen to your medical team and talk to close family and friends. Outline your goals and make your decision based on them.

If you are diagnosed with mesothelioma, there are legal avenues to seek compensation. This includes lawsuits, settlements, and asbestos trust funds. A qualified mesothelioma lawyer can help you navigate your resources and help you make a case.