Malignant Epithelial Mesothelioma

The characteristics of your cancer, even at the cellular level, can have a huge impact on your prognosis. Learn about epithelial mesothelioma, a common cell type that responds especially well to treatment.

Epithelial mesothelioma distribution

Epithelial mesothelioma accounts for 50 to 70 percent of all diagnosed cases.

The cellular makeup of a mesothelioma tumor can vary substantially from patient to patient. Malignant epithelial mesothelioma, a specific cellular type of the disease, accounts for 50 to 70 percent of all diagnosed cases. If your tumor is mainly composed of epithelial cells, you may respond better to treatment and receive a more favorable outcome than patients with other cell types. Knowing its characteristics, how it is diagnosed and its most effective treatment options will help you understand how cell type can affect your prognosis.

Because it represents the majority of cases, doctors have performed more research on epithelial mesothelioma than any other cell type. During cancer research, doctors study cell types to better understand how well patients will respond to specific treatments. Although treatment does not typically differ from one cell type to the next, your type may dictate which clinical trials are available to you.

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Tumors can be classified by the type and appearance of the cancerous cells involved. Epithelial cells form the epithelium, which is the most common of the four major tissue types in humans. With functions including protection, sensory perception and fluid secretion, epithelial tissue lines several major body cavities and most of our organs. Epithelial cells are also present in our skin, eyes, taste buds and ears.

The structure of epithelial tissue will vary depending on its location and function. The epithelial cells may appear thin and flat, cube- or hexagon-shaped or tall and column-like. When the epithelial cells turn cancerous, they can take on several visual patterns. Usually they lose uniformity or otherwise become atypical in appearance, but they can also form small tubes or clusters that resemble a raspberry. Once epithelial cells become cancerous they are called epithelioid cells. Epithelioid cells occur more commonly in cases of malignant pleural mesothelioma rather than peritoneal mesothelioma.

Because epithelial cells lack mobility and adhere closely together, they are less likely to spread to distant locations like sarcomatoid cells. Cancerous epithelial cells primarily spread to nearby lymph nodes and from there migrate locally via the lymphatic system. Conversely, sarcomatoid cells are loosely organized, and they can migrate easily, leading to quicker metastasis.

A certain type of epithelial mesothelioma occurs more commonly in women, and it’s known as well-differentiated papillary mesothelioma. No other cell type is associated with a particular gender, age or race.

How It Is Diagnosed

Epithelial cancer cells cannot be identified with diagnostic imaging scans. To determine which cell type is present, a thoracoscopy or similar form of surgical biopsy needs to be performed. Biopsies offer doctors a way to examine the potentially cancerous cells under a high-powered microscope. During a biopsy, a tissue sample of the tumor is extracted for further evaluation of the cells it contains.

One of the primary challenges of diagnosing epithelioid mesothelioma is distinguishing it from other types of cancer. Epithelial tumors are often confused with adenocarcinoma, a common type of cancer that develops in the lungs, breasts and colon. Glandular mesothelioma, an epithelial cell subtype, may resemble adenocarcinoma of the lungs. It may be difficult to differentiate these two conditions.


Immunohistochemistry is a process that detects proteins called antibodies on the surface of cells. These proteins help classify a cancer’s cell type. Pathologists use immunohistochemistry to identify epithelial mesothelioma and differentiate it from adenocarcinoma. Immunohistochemistry is used less often to differentiate sarcomatoid mesothelioma from other sarcomatoid tumors.

Some of the antibodies that help diagnose epithelial mesothelioma include calretinin, CK5/6, WT-1, D2-40, TTF-1 and BerEP4. Calretinin is considered the most sensitive and specific antibody for mesothelioma. It is present in the majority of epithelial mesothelioma cases.

The specific cell type will be revealed in your doctor's pathology report. If you haven't been told your cell type yet, just ask your doctor and request a copy of the pathology report for your records.

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Additional Resources

Karen Selby is a registered nurse and a Patient Advocate at The Mesothelioma Center. She worked in several subspecialties within nursing before joining in 2009.

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