It may take a number of consultations and tests before the correct diagnosis is made. However, an accurate diagnosis is necessary so that patient can receive the appropriate treatment, not only for the disease itself, but also for the stage of the tumor.
Some Tests do not Rule out the Possibility of Mesothelioma Misdiagnosis
Initially the doctor may perform a thoracentesis and/ or a closed pleural biopsy to obtain a sample of the pleural fluid and/or a sample of the tissue in the pleura because the patient presents with shortness of breath. This can establish the fact that a pleural malignancy exists, but it may not provide enough tissue to distinguish mesothelioma from lung adenocarcinoma, which is similar in appearance. Also, the tissue obtained from a closed pleural biopsy is not sufficient to determine whether the mesothelioma tumor contains epithelial, sarcomatoid, or biphasic cells.
Sometimes these procedures may have an adverse effect. A small percentage of patients may develop “seeding” along the biopsy site, meaning tumor cells will implant themselves and the patient will experience a recurrence of the disease in the chest wall. This is typically prevented through the use of radiation that is administered to the site where the biopsy/thoracentesis was performed. Localized radiation is also used to treat seeding if it occurs.
Additional Tests are Needed to Prevent Mesothelioma Misdiagnosis
The doctor may also perform a bronchoscopy along with the other procedures to distinguish between mesothelioma and lung adenocarcinoma. In this procedure, an endoscope, which is a long slender tube with a light and a magnifying lens, is introduced into the airways that conduct air into the lungs so that the doctor can view inside. The reason this is helpful in making a definitive diagnosis is because abnormal tissue on the lining of these airways is characteristic of adenocarcinoma, but not of mesothelioma.
Another testing methodology that is still being developed is immunohistochemistry (IHC). It uses antibodies that bind to specific proteins in the cells of tissues. These antibodies contain a compound that appears as a colored deposit when looked at under a microscope.
In a study titled “Identification of Novel Markers for the Diagnosis of Malignant Pleural Mesothelioma”, published March 2011 in The American Journal of Pathology, researchers obtained cell lines found in fluid from both malignant pleural mesothelioma and lung adenocarcinoma. They used these cells to perform an analysis that resulted in the identification of genes that had distinct markers.
They started by using immunohistochemical staining with anti-type III collagen antibodies on tumor cells that had been biopsied. They found that it showed a positive labeling for mesothelioma cells but not for adenocarcinoma cells. They then performed another type of test that detects proteins and antigens, called an enzyme-linked immunosorbent assay (ELISA). This test showed that the C-C motif chemokine 2 (CCL2) concentration was present in 61 of the samples taken from mesothelioma patients, 25 of the samples from adenocarcinoma patients, and 15 of the samples from patients with fluid that had no element of disease. CCL2 is a gene located on chromosome 17 and it recruits a particular type of white blood cells to a site where there is injury or inflammation.
The researchers also discovered that the galectin-3 concentration was lower in the mesothelioma samples than it was in the samples taken from the patients with lung adenocarcinoma, or those who had no disease. Galectin-3 is a protein that binds to sugar that is encoded in the LGALS3 gene located on chromosome 14. It is also associated with inflammation.
These findings led researchers to conclude that “type III collagen, CCL2, and galectin-3 are promising new diagnostic markers for mesothelioma.”