Malignant pleural mesothelioma is the most common type of mesothelioma, making up over two-thirds of all cases. Pleural mesothelioma affects the lining of the lung and chest cavity known as the pleura.
The pleura is is the membrane that surrounds the chest and lungs. This membrane, known as the mesothelium, lines several body cavities. While the pleura surrounds the lungs, cancer of the pleura is not actually lung cancer (which may also be caused by asbestos exposure).
Pleural mesothelioma, like all kinds of mesothelioma, can be difficult to diagnose or easily misdiagnosed. If you are aware of prior asbestos exposure, it is important to inform your physician so that mesothelioma symptoms can be correctly identified.
Causes of Pleural Mesothelioma
Asbestos causes pleural mesothelioma. Used in a variety of industrial and construction applications, asbestos fibers are small, lightweight, strong, and easily airborne.
Once in the air these fibers are easily inhaled or injested, their size and sharp shape makes it easy for them work their way into the smallest passageways of the lungs and then into the pleura. Asbestos fibers thwart the body's natural defenses. Whether it is the sharp shape of the asbestos fibers, an unknown chemical reaction, or a combination of both these factors that cause the mesothelial cells of the pleura to become abnormal and divide without control is unknown. The connection, however, between asbestos and pleural mesothelioma has been clear since the begining of the 1960s.
Asbestos is the single largest cause of occupational cancer in the US1. In addition to pleural mesothelioma, asbestos causes lung cancer, other forms of mesothelioma, including peritoneal mesothelioma, and it is linked to several other types of cancer such as colon, stomach, throat, and laryngeal cancer.
In addition, absestos causes several non-cancerous conditions such as asbestosis, pleural effusions, pleural plaques, and pleural thickening (also known as pleural fibrosis). The majority of those diagnosed with these non-malignant conditions do not develop mesothelioma. However, the asbestos exposure levels associated with these conditions is an important factor to take into account when considering your risk of developing pleural mesothelioma.
Pleural Mesothelioma Symptoms
"Do I have pleural mesothelioma?" If you have been asking yourself this question, chances are you have a history of asbestos exposure.
Pleural mesothelioma's symptoms are not specific, and may indicate other, less serious, conditions. However, if you know you have a history of asbestos exposure, it is wise to be proactive regarding your health care choices and observant of potential symptoms of pleural mesothelioma. Have regular check ups with your physician and make sure he or she is aware of your concerns and your history of asbestos exposure.
Pleural mesothelioma is a dose-dependent disease, meaning that the longer and more heavily your exposure to asbestos, the greater the chance you have of developing pleural mesothelioma (or another type of mesothelioma). This dose-dependence can also affect how quickly you are diagnosed with pleural mesothelioma, although the disease is known for its long latency periods of 10, 20, even as many as 40 years from exposure to disease progression.
Symptoms of Pleural Mesothelioma
Symptoms of pleural mesothelioma may include, but are not limited to:
- Breathlessness (dyspnea)
- Along with shortness of breath, patients may suffer from a cough. Rarely, patients may develop hoarsness or cough up blood (hemoptysis).
- Chest pain
- Chest pain is often nonspecific, and may sometimes be felt in upper abdomen, shoulder, or arm. Chest pain and breathlessness are the most common, and usually earliest presenting, symptoms of pleural mesothelioma
- Weight Loss
- Unexplained weight loss is cited as a symptom in about a third of pleural mesothelioma cases.
- Pleural effusion
- A pleural effusion is the result of too much fluid building up between the parietal and visceral pleura (linings of the chest and lungs, respectively); a pleural effusion may cause chest pain and difficulty breathing (dyspnea), however, many cause no symptoms and are first discovered during the physical examination or seen on a chest x-ray.
- Night sweats
- Less common, but still cited enough to be considerd a symptom of pleural mesothelioma are fever, chills, and night sweats.
Pleura Mesothelioma Diagnosis
Pleural mesothelioma, while the most common type of mesotheioma, is still a rare diagnosis. It is important that you seek out specialists who can effectively diagnose any symptoms suspected of indicating pleural mesothelioma. Many patients begin exhibiting symptoms for several months before addressing them with their physician; once in the care of a doctor, pleural mesothelioma is still somewhat tricky to diagnose, thanks to its rarity and nonspecific symptoms. While not surprising that early diagnosis is tricky, if you have a history of risk factors and concerns regarding an unusual symptoms, visit your doctor; ask about your concerns regarding pleural mesothelioma.
Diagnosing Pleural Mesothelioma
A physical exam and patient history will likely be your doctor's first step in diagnosing pleural mesothelioma. Past exposure to asbestos is a strong risk factor for pleural mesothelioma and the longer and more seriously you were exposed to asbestos, the greater your risk. If your doctor does not ask about your work history and potential mesothelioma risk factors, let him or her know about your asbestos exposure.
The next step is usually an x-ray of the chest. Pleural effusions, masses, and scarring may be seen on x-rays. Because x-rays are less sensitive than newer imaging techniques, an abnormal finding on an x-ray will likely prompt your physician to order further imaging through a CT or CAT scan or MRI. This will likely provide a better idea of the size, location, and invasiveness of the mass, but not a definitive diagnosis, nor a complete picture of if the mesothelioma has metastized into the lymph system.
Once a suspicious mass or fluid has been spotted, your doctor will probably order a thoracentesis and/or biopsy be performed.
Thoracentesis is a minimilarly invasive procedure where fluid is removed from the pleural space. As many as 95% of patients with pleural mesothelioma have pleural effusions, or excess fluid collection in the pleural space. Thoracentesis (or thoracocentesis) is generally an outpatient procedure and usually requires only local anesthestic. A hollow needle or catheter is interted into the chest to drain the accumuated fluid.
Generally the first biopsy, or tissue collection, performed is a fine-needle aspiration biopsy. Using a thin, hollow needle, cells from the suspcious mass are extracted. Like the thoracentesis, it is not as invasive as many surgical procedures and can help avoid the need for diagnostic surgery.
The collected fluid and/or biopsy tissue will then be sent for analysis by pathologist and/or cytologists. These specialists will look for signs of cancerous cells in the samples. Immunohistochemistry is the chemical staining of these samples to better identify abnormal cells. "Immunos," as these tests are sometimes called, are an important form of testing and are usually recommended.
If a definitive diagnosis has still not been reached, more invasive testing may be required. Your doctor may perform a thoracoscopy; this involves inserting a lighted scope, sometimes with a camera on it, into the chest for a closer look. If suspicious masses are seen, the doctor may cut out a sample of tissue to be examined for maligant cells.
Recent Pleural Mesothelioma Journal Articles:
- 1. American Thoracic Society. American Thoracic Society Documents. 2004 Vol 170. pp 961-715. Diagnosis and Initial Management of Nonmalignant Diseases Related to Asbestos.
- Nguyen GK. American Journal of Clinical Pathology. 2000 Nov;114 Suppl:S68-81. Cytopathology of pleural mesotheliomas. Division of Anatomical Pathology, University of Alberta Hospitals, Edmonton, Canada.