Epithelial or Epithelioid mesothelioma cells are the most common of the three mesothelioma cell types.
An examination of these diseased cells under an electron microscope shows that epithelioid mesothelioma is formed by the connection of small to medium sized cube-shaped cells that have round, uniformly shaped nuclei. Each cell’s nucleus contains a nucleolus, which is a structure that is not surrounded by a membrane, and that is made up of proteins and nucleic acids. The nucleolus is importance because this is where Ribosomal RNA is made. Ribosomal RNA is the mechanism that takes the information from messenger RNA concerning what amino acids are needed to create the proteins that keep the epithelioid cells growing.
Epithelioid mesothelioma may sometimes appear as sheets of polygon-shaped cells that closely resemble the cells that make up large cell lung carcinoma. For this reason, epithelioid mesothelioma may be misdiagnosed.
One of the ways that pathologists, doctors who analyze tissue samples to help diagnose a disease, try to minimize the chances of misdiagnosing epithelioid mesothelioma is by finding markers that indicate the disease is/is not present. Markers, sometimes called biomarkers, are naturally occurring molecules or genes within the body that indicate the presence of a particular disease.
When pathologists analyze the tissue sample to see if it is epithelioid mesothelioma, they will use a process called immunohistochemistry. The basic principal that explains how this process works is that antibodies bind to particular antigens within the tissue. An antibody is a type of protein that the immune system sends out to identify and inhibit a foreign body. An antigen is the foreign substance that has come into the body. What this mean is, if there are epithelioid cells present, the immune system will send out the specific proteins that stop them. The pathologist looks for those proteins.
Meta-analysis of Scientific Literature Indicates Some Recently Discovered Markers that Can Help in the Diagnosis of Epithelioid Mesothelioma
In an article titled “Immunohistochemical Diagnosis of Epithelioid Mesothelioma: An Update”, published November 2005 in the Archives of Pathology & Laboratory Medicine, the researcher explains the results of his meta-analysis of all of the existing scientific literature on the subject of markers used to diagnose epithelioid mesothelioma. A meta-analysis is a systematic review of a number of different published studies that are looking at the same issue. The data that is collected from these studies is compared by using specific statistical methods.
The researcher who conducted this meta-analysis found that:
- There were specific positive markers that were useful in diagnosing epithelioid mesothelioma, meaning they are present when this cell type is present. They include: calretinin, keratin 5/6, D2-40, podoplanin, mesothelin, and Wilms tumor 1 protein.
- There were specific negative markers, meaning they are indications that it is not epithelioid mesothelioma. They include: carcinoembryonic antigen, MOC-31, B72.3, and Ber-EP4.
- The two most helpful markers in diagnosing epithelioid mesothelioma are D2-40 and podoplanin. They are highly sensitive and specific for this cell type. However, their usefulness has not been fully determined in routine diagnostic work.