Malignant Epithelial Mesothelioma

n terms of cellular histology, there are four different types of mesothelioma cells: epithelial, sarcomatoid, biphasic (mixed), and desmoplastic (considered a variant of sarcomatoid). Epithelial mesothelioma is the most common of the four types of malignant mesothelioma, occurring in approximately 50 to 70 percent of cases.

There are numerous subtypes of epithelial mesothelioma, including:

• Tubulopapillary
• Glandular
• Histiocytoid
• Adenoid cystic
• Microcystic
• Macrocystic
• Signet Ring
• Single File
• Diffuse – NOS
• Glomeruloid
• Small Cell
• Poorly Differentiated (large cell) or Pleomorphic
• Deciduoid
• Mucin Positive
• Gaucher Cell-Like
• In Situ
• Well-Differentiated Papillary

Epithelial mesotheliomas are commonly referred to as epithelioid mesothelioma. An epithelioid cell is a mesenchymal cell whose morphology resembles that of epithelial cells. Epithelioid mesothelioma cells are given this name because they have the appearance of epithelial cells when viewed under a microscope (the suffix "-oid" indicates resemblance or similarity). These are cells that line structures and cavities located throughout the body.

Mesothelial cells are themselves a type of epithelial cell and it is these cells that become cancerous when malignant mesothelioma develops within the pleura, peritoneum, or pericardium. Epithelial mesothelioma cells tend to have a well-defined, uniform shape when viewed under a microscope.

An important point to note is that malignant epithelioid mesothelioma cells very closely resemble cells of another type of cancer known as adenocarcinoma, which can develop in the lungs or in other vital organs. This type of cancer also originates in epithelial tissue. When adenocarcinoma develops in the lungs, it can often spread to the mesothelial lining of the lungs (the pleural membrane).

For these reasons, those diagnosed with adenocarcinoma that have been exposed to asbestos in the past should seek a second opinion to ensure accurate diagnosis.

Prognosis and Treatment

Generally, each of the types of mesothelioma are treated the same way, as mesothelioma treatment is based on the location and stage of the cancer, rather than the types of cells involved.

However, there are distinct differences in the way each type of cancer responds to treatment. In general, patients with malignant epithelioid mesothelioma have a better prognosis than patients with either sarcomatoid or biphasic mesothelioma, thus treatment may not be as aggressive.