Pleural mesothelioma appears as a firm, grayish tumor that settles on the pleural surfaces that cover the lung and line the inner surface of the chest wall. It also develops hidden nodules and a buildup of fibrous tissue. It may completely blanket the lung with a rind of tumor that can be as thick as five centimeters even though the tumor has only slightly penetrated the bulk of the lung.
During the early stages, the tumor invades the chest wall, the fluid-filled sac surrounding the heart and the diaphragm. There can also be involvement of the lymph nodes in the area between the lungs.
Pleural mesothelioma is classified into three cell subtypes:
- Epithelioid cells are the most common, making up 50 to 60 percent of all cases. These cell types present as elongated nipple-like structures that are uniform in shape. They are less aggressive, meaning this type of pleural mesothelioma has the best prognosis.
- Sarcomatoid cells are the least common. They present as elongated spindle-shaped cells that are irregularly shaped and overlap one another. These cells are the most aggressive, resulting in a poor prognosis.
- Biphasic or mixed cells have both epithelioid and sarcomatoid features.
Whom Does Pleural Mesothelioma Affect?
A mesothelioma diagnosis such as this affects men 4-5 times more often than women according to the Surveillance Epidemiology and End Results database, part of the National Cancer Institute. The database also shows that the majority of patients who present with the disease are 50-80 years of age.
That’s because patients typically develop mesothelioma 20-60 years after asbestos exposure.
What are the Symptoms?
The most common symptoms of pleural mesothelioma include shortness of breath, cough, and sometimes pleurisy (inflammation of the pleural membrane) and chest pain.
Most cases are usually identified with chest X-rays that demonstrate a pleural abnormality in one lung in combination with a large buildup of fluid between the layers of the pleura. Approximately 60 percent of these patients will have a right-sided tumor and about five percent will present with disease in both lings. There are also those patients that present with the lung on the affected side trapped by a thick rind of tumor.
Some patients don’t have fluid buildup. Instead, they present with a pleural mass or widespread pleural thickening. Most patients will experience symptoms of fibrous tissue buildup on the pleural surface, calcifications and a substantial loss of lung volume on the affected side.
How is Pleural Mesothelioma Diagnosed?
Oftentimes the examination of the pleural fluid doesn’t indicate that there is a malignancy and mesothelioma can be misdiagnosed. Pathologists using a light microscope may mistake mesothelioma cells for adenocarcinoma cells, which are similar in appearance to epithelioid cells.
That is why at the 2006 biennial meeting of the International Mesothelioma Interest Group pathologists with an interest in the field worked together to develop the following recommendations for a diagnosis of mesothelioma:
- Use of biomarkers that have a greater than 80 percent sensitivity or specificity for the tumors that are being diagnosed.
- Determining positivity for the disease by taking into account whether the cell stain being examined came from the nucleus or cytoplasm and the percentage of cells affected by the staining process.