Mesothelioma Diagnosis and Mesothelioma Detection
Malignant mesothelioma detection, like other cancers, can be accomplished with imaging equipment, such as x-ray machines. But once detected, mesothelioma diagnosis is difficult for a number of reasons. First, there is a very extended time period between the exposure to asbestos and the onset of the disease, sometimes as long as 50 to 60 years. Until recent years, patients were unaware of the risks related to asbestos exposure, and therefore didn’t think to inform their doctors of asbestos-related jobs they held many years earlier.
Second, the typical symptoms of mesothelioma, shortness of breath and coughing, are also symptoms of many other types of lung problems, both cancerous and non-cancerous. Thus, just because a person has these symptoms, it does not in any way provide a mesothelioma diagnosis.
Third, many types of tumors can exist in the serous cavities that are not mesothelioma. These other types of tumors can be non cancerous, or benign, that originate in the tissues of the serous membranes, other than the mesothelium. Or they can be tumors that have migrated from other organs with cancerous growths due to metastases.
X-rays and other types of imaging technologies can be used to detect tumors or effusion (build up of fluid) in the body, including mesothelioma detection. A growth in the chest cavity will show up in an X-ray or MRI analysis. But these devices cannot directly determine the type of cancer or provide a mesothelioma diagnosis. They cannot determine whether the tumor is mesothelioma or originates from some other source.
Positron emission tomography (PET) is a type of diagnostic imaging scan that is used for malignant mesothelioma detection. PET scans use the emission of positrons (tiny particles that are emitted from radioactive substances) for the purpose of radiation detection.
Some medical professionals are of the impression that PET scans are the most effective method through which to definitively verify a case of mesothelioma. While they believe that standard imaging techniques like x-rays and MRIs should continue to play a role in diagnosing the disease, it is felt that positron emission tomography is becoming an increasingly valuable tool in the staging and typing of the latent asbestos cancer.
To provide a mesothelioma diagnosis, a biopsy is needed. This biopsy then undergoes what is called diagnostic histopathology. Histopathology is a technique where the cells from the tumor are viewed under a high-powered microscope, or electron microscopy. Electron microscopy is considered the gold standard for evaluating tumor material from a biopsy. It is a highly advanced microscope that allows viewing of the tiniest elements of cell tissue.
For mesothelioma diagnosis, a pathologist (a doctor who specializes in disease detection) places the tumor cells under the electron microscope and then views the structure of the individual cells. The mesothelioma cells have a specific shape and pattern. But mesothelioma cells also look similar to other types of cancer cells, such as adenocarcinoma cells, and this can make the pathologist's job very difficult. Even with the electron microscope, the different types of mesothelioma cells can be hard to recognize. The three types of cells are epithelioid mesothelioma cancer cells, which are tubular in shape, sarcomatoid mesothelioma cancer cells, which are oval and irregularly shaped, and biphasic mesothelioma cancer cells, which are a combination of shapes. These cells can be confused with other types of cancer cells.
Due to this diagnostic confusion, much research is underway to find new methods for diagnosis. One method is to evaluate the types of compounds generated by the mesothelioma cancer cells. This is called histochemistry. Histochemical reactions have long been used to distinguish between mesothelial and other types of tumor cells. For example, mesothelial cells are known to produce specific types of carbohydrate compounds. Unfortunately, other types of cells in the body also produce these compounds.
Immunochemistry is also being used to detect mesothelioma. This area of study evaluates the presence of antibodies in the body. Certain types of antibodies are known to be associated with certain types of cancer. But mesothelial cells have no specific types of antibodies that can provide a "positive" marker. Consequently, immunochemistry allows the doctor to "eliminate" the other cancers, but does not indicate the presence of mesothelioma. These techniques offer insight into the disease and may help eliminate other diseases, but none can directly detect mesothelioma.
SMR Protein: Recently, because of the difficulty in diagnosing malignant mesothelioma, research has concentrated on finding new ways to detect the presence of the disease. Researchers in Australia have found that a certain protein, called SMR or Soluble Mesothelin Related protein, is elevated in patients with mesothelioma. These researchers have suggested that a test for the presence of SMR in the blood could represent a useful marker for the diagnosis and disease progression. They feel that such a diagnosis tool could lead to earlier detection, and thus more effective treatment.
One of the most striking findings of their research was that several asbestos-exposed persons who tested positive for SMR were diagnosed with mesothelioma within three years. They suggested that evaluation of SMR may help to identify persons at risk for this deadly disease. Also, they found that SMR levels increase as mesothelioma progresses, suggesting that SMR evaluation could be used to track the progression of the disease and the effectiveness of treatment.
Osteopontin Glycoprotein: In an effort to produce the first early-detection test to screen for malignant mesothelioma, researchers at Wayne State University have been studying the possible link between mesothelioma development and levels of a glycoprotein called osteopontin. Early clinical study findings of 190 patients have demonstrated a link between high levels of osteopontin and the development of malignant pleural mesothelioma.
Although the results are being viewed as preliminary, there is a great deal of excitement surrounding the potential of a blood test capable of screening for mesothelioma in its earliest stages. While there is no known cure for malignant mesothelioma, research is ongoing and certain successes have already been realized in terms of extending survival time beyond the one to two year post-diagnosis average. It is hoped that if mesothelioma specialists have more time to conduct treatment on a lesser developed form of the asbestos cancer, patients will have a greater chance of survival.
Despite the fact that the preliminary results of the osteopontin blood test clinical trial have been met with some controversy, the National Cancer Institute (NCI) continues to sponsor additional study.
Tell Your Doctor About Asbestos Exposure
If you or a loved one has been exposed to asbestos, even if it was in the distant past, it is very important that you inform your doctor. One reason why mesothelioma is such a deadly disease is that it is detected late in the disease process. If your doctor knows of the exposure, he or she may be more aware of your symptoms or other health issues that could be used for early detection and a more optimistic mesothelioma prognosis.
[Page updated August 2006]