Mesothelioma and pleural thickening are lung diseases that can arise from exposure to asbestos. However, pleural thickening can be found in several other types of lung disease as well, unrelated to asbestos. Below are relevant facts about pleural thickening and mesothelioma, their similarities and differences, and diagnostic implications.
What is Pleural Thickening?
Pleural thickening, also known as diffuse pleural thickening (DPT), occurs when the lining of the lung, or the pleura, becomes scarred and thickens. This process happens as a result of intense inflammation caused by insult or injury to the lungs.
In its early stages, DPT has little to no symptoms. However, as pleural thickening worsens due to more extensive scarring, it becomes more challenging to expand the lungs fully. The most common symptoms are chest pain and dyspnea (shortness of breath). (Asbestos.com)
Other symptoms may include:
- Difficulty with inspiration
- Pain with coughing
- Dull, long-term chest pain
- Diminished pulmonary function
What Causes Pleural Thickening?
One of the most common causes of pleural thickening is prolonged exposure to asbestos. The microscopic fibers of asbestos can get stuck in the pleura, which triggers an inflammatory response and fluid build-up. Over time, scar tissue develops, and this is known as pleural thickening.
One study showed that 5% to 13.5% of asbestos-exposed workers had pleural thickening in their lungs. (Asbestos.com) Another study found that a majority of first-responders who were exposed to asbestos during the World Trade Center attacks had DPT on imaging of their lungs. (Hoz, 2019)
After exposure to asbestos, pleural thickening can take as little as one year to as long as many decades to develop. Much of the time, the latency period between exposure to asbestos and the detection of DPT is between 15 and 20 years.
Aside from asbestos, DPT can be caused by other diseases that cause acute lung inflammation such as:
- Empyema (build-up of pus in the pleural space)
- Pleural hemorrhage (accumulation of blood in the pleural space)
- Chronic pneumonia
- Radiation exposure
- Pulmonary embolism
Since pleural thickening can have many causes that require very different treatments, a history of asbestos exposure is crucial for helping your doctor come to the right diagnosis. (Asbestos.com)
Comparing Pleural Thickening and Mesothelioma
Both pleural thickening and mesothelioma can be caused by asbestos exposure. However, the main difference between the two is that mesothelioma is a type of cancer.
There are four types of mesothelioma: pleural mesothelioma, pericardial mesothelioma, peritoneal mesothelioma, and testicular mesothelioma. Pleural mesothelioma is the most common type and is usually caused by exposure to asbestos. (Mesothelioma.com)
One important note is that pleural thickening can be a result of mesothelioma, and is usually the most common CT scan finding associated with the disease. Similar to DPT, when a person inhales asbestos fibers, it can cause an inflammatory response in the pleural lining of the lung. In the case of mesothelioma, malignant mesothelioma cancer will develop. (Asbestos.com)
The typical age group of mesothelioma patients is 60 years old or older. It typically presents decades after asbestos exposure, with gradually worsening, nonspecific, respiratory symptoms such as:
- Chest pain
- Night sweats
- Dysphagia (trouble swallowing)
- Lumps under the skin on the chest
In patients with more advanced disease, systemic symptoms such as fatigue and weight loss may be present.
In rare instances, mesothelioma may invade vital structures such as the spinal cord, the bowels, or the heart and cause more acute symptoms such as neurological deficits, abdominal pain or constipation, and heart failure, respectively. (UpToDate.com)
It is important to tell your doctor about any mesothelioma symptoms you are having as it will help to stage your disease and guide treatment.
Diagnosing Mesothelioma and Pleural Thickening
Aside from a thorough patient history and physical examination, imaging is usually the best way to diagnose pleural thickening. For mesothelioma, a history, physical exam, imaging, and sometimes a biopsy are all helpful diagnostic tools.
The most common imaging studies to diagnose both DPT and mesothelioma are X-rays, magnetic resonance imaging (MRI) scans, and computed tomography (CT) scans.
With an X-ray, a likely finding of DPT includes an irregular wedge-shaped density that usually involves the apex or uppermost portion of the lung. (Saito, 2019) Moreover, it can sometimes extend to at least 25% of the entire chest wall. (Asbestos.com)
In terms of mesothelioma, X-ray findings may show a pleural mass on one side of the lung, with pleural effusion, or fluid. Another finding is diffuse pleural thickening in the absence of pleural effusion. Also, pleural plaques, which are different from pleural thickenings, are commonly seen. (UpToDate.com)
Diffuse pleural thickening on a CT scan will present as a white thickening on the outside of the lung, usually exceeding 3 mm, with spots of calcification. (UpToDate.com) The most common finding on a CT scan of mesothelioma is pleural thickening. However, other findings such as thickening on the inside of the lung, pleural effusions, chest wall involvement, rib destruction, and pleural plaques can also be seen as well. (UpToDate.com)
Another use of a CT scan is to determine the severity of mesothelioma, especially in disease that has metastasized. Also, MRI and a positron emission tomography (PET) scan can improve the evaluation of metastatic spread and, likewise, help distinguish between pleural thickening and pleural thickening associated with mesothelioma.
Mesothelioma and Pleural Thickening Prognosis
Pleural thickening is considered to be a benign disease. However, there is a possibility that patients can go on to develop mesothelioma. The prognosis of DPT depends on its severity at the time of diagnosis, and without careful monitoring using serial physical exams, imaging, and pulmonary function testing, DPT may progress and become more serious. (UpToDate.com)
Like many cancers, mesothelioma can either be benign or malignant. Benign mesothelioma is rare, non-cancerous, and not linked to asbestos exposure. (Mesothelioma.com) Pleural mesothelioma, on the other hand, is usually malignant and generally has a poor prognosis. The overall survival is approximately 9 to 17 months after diagnosis and decreases with time.
Pleural Mesothelioma Survival Rates Over Time:
- 1-year after diagnosis: 73%
- 3-years after diagnosis: 23%
- 5-years after diagnosis: 12%
- 10-years after diagnosis: 4.7%
The strongest prognostic factors for malignant pleural mesothelioma are the cancer stage, the cell type (histology), and the patient’s gender and age. Most mesothelioma is of the epithelioid cell type, which is the most common cell type and usually has the best prognosis. The two other cell types, sarcomatoid and biphasic, are rarer and have a worse prognosis. (Mesothelioma.com) Also, advanced cancers that are more difficult to resect surgically, as well as men older than 75 years, have a poorer prognosis. (UpToDate.com)
Differences in Treatment Between Both
Diffuse pleural thickening is usually treated supportively, and, in most cases, doctors will provide individual symptomatic management.
Prescription medication, such as bronchodilator inhalers or steroids, can help patients breathe more easily. Also, pulmonary rehabilitation and preventative measures such as smoking cessation are helpful as well. One study showed that pulmonary rehabilitation, which involves physical activity to help overcome breathing difficulties, improved the symptoms of pleural thickening. Smoking reduces lung function and should be stopped in all patients with DPT.
Also, a surgical procedure, known as a pleurectomy, may be performed in more progressive cases.
The goal of treatment in DPT, aside from preventing disease progression, is to help ease symptoms and increase the quality of life of patients. (Asbestos.com)
For mesothelioma, treatment usually includes any combination of surgery, radiation therapy, and chemotherapy. This multimodal approach is determined by the stage of the disease and the cell type. In general, treatment is intended to slow the progression of the disease, not cure it.
Although medical advances have helped improve patient’s response to chemotherapy, the rate of success of such treatment remains low.
Promising new therapies, such as immunotherapy, gene therapy, and photodynamic therapy, are intended to help fight disease more effectively while minimizing side effects. Moreover, these treatments have shown success in increasing the life span of patients in different clinical trials. (Mesothelioma.com)
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