The most frequent type of mesothelioma is epithelioid mesothelioma, which is caused by asbestos. The lining of the lungs, abdomen, or heart can develop epithelial mesothelioma cells. Patients might expect to live one to two years if they receive treatment.
What Is Epithelioid Mesothelioma?
Epithelial cells are one of the four types of tissues found in the human body. On the surface of the skin, in the linings of hollow organs and blood arteries, and along the lining of interior cavities, epithelial tissue can be found.
When epithelial cells are exposed to asbestos fibers, they can mutate and become malignant. The most prevalent type of mesothelioma is epithelioid mesothelioma. Around 70–80 percent of all mesothelioma cancer patients have this cell type.
Normal epithelial cells differ in shape and can be found in single or multiple layers, depending on where they are located in the body. When the cells mutate, they may also develop in the lining of the lungs, abdomen or heart.
Epithelioid cells can present in a variety of shapes, including:
- Squamous (flat)
Squamous cells are commonly found in the lining of the lungs, also known as the pleura.
Epithelioid mesothelioma cells are also recognizable compared to other mesothelioma cell types because of how they adhere to each other. The cells form in small clusters and may be round or oval. The cells can also be identified by their visible nuclei.
Epithelioid cells typically divide faster than other cells. However, due to the way the cells form in clusters, they are slower to metastasize compared to other cell types.
Epithelioid Mesothelioma Symptoms
Depending on where the cancer grows, epithelioid mesothelioma can cause a range of symptoms. The presence and intensity of symptoms are also influenced by the patient’s overall health, age, cell type, and diagnosis stage.
Common Symptoms of Epithelioid Mesothelioma
- Abdominal or chest pain
- Anemia (low iron)
- Coughing and hoarseness
- Difficulty breathing
- Fever and fatigue
- Fluid buildup near the lungs or abdomen
- Low blood oxygen levels
- Nausea and vomiting
- Unexplained weight loss
Diagnosing Epithelioid Mesothelioma
The diagnostic process for epithelioid mesothelioma typically begins with a series of imaging tests. These tests may include X-rays, CT scans, PET scans or MRIs. If a tumor or abnormality is detected, a blood test may be ordered. Blood tests can identify specific biomarkers to determine if mesothelioma cells are present.
A biopsy will be performed to confirm a diagnosis. A biopsy can be a non-surgical or surgical procedure to remove a tissue sample for analysis. Lab tests can determine the type of mesothelioma cells, as well as identify stage and malignancy.
A pathologist may also perform an analysis called immunohistochemistry, which is a staining technique that uses various antibodies to test for particular antigens in cell tissue. Immunohistochemistry can identify cell type and differentiate mesothelioma from other malignancies, such as adenocarcinoma.
Antibodies including calretinin, D2-40 and WT1 are used to identify epithelioid mesothelioma in patients. When these antibodies are applied in combination, they can help a pathologist accurately diagnose the disease.
Rare Epithelial Cell Types
In addition to the common epithelioid cell type, pathologists have identified various rare subtypes that develop in some patients. These subtypes may have limited treatment options and worse prognoses compared to standard epithelial mesothelioma.
- Adenomatoid mesothelioma: Adenomatoid cells, also known as glandular or microglandular mesothelioma, form in glandular structures. The cells are commonly flat or cubed shape and can be benign or malignant.
- Adenoid cystic mesothelioma: This rare form of mesothelioma is most commonly found in the peritoneal or pleural cavities. Cystic cells are often benign, though malignancies can sometimes form. Cystic mesothelioma is more commonly diagnosed in young women, particularly those of child-bearing age.
- Deciduoid mesothelioma: This rare form of mesothelioma typically develops in the abdomen, but it can also form in the lining of the lungs. The cancer’s exact cause is currently unknown, and it is most often diagnosed in women.
- Well-differentiated papillary mesothelioma (WDPM): This type of mesothelioma is not related to asbestos exposure and usually affects young women. It can form in the pleura, peritoneum and genitals of men and women. Papillary mesothelioma is slow to metastasize. Studies have found survival times ranging from 36 – 180 months.
- Small cell mesothelioma: This subtype is sometimes mistaken for small cell lung cancer. It forms in the peritoneum and pleura. Small cell mesothelioma is usually diagnosed in biphasic tumors, which contain epithelial and sarcomatoid cells.