Mesothelioma is a rare cancer that is caused almost exclusively by exposure to asbestos. It affects the thin, protective membrane surrounding the lungs, heart and abdominal cavity. An estimated 3,000 cases annually are diagnosed in the United States, and the majority of those are traced to an occupational exposure.
Although the use of asbestos has been reduced dramatically in recent decades, the incidence of mesothelioma has remained steady. It can take anywhere from 20 to 50 years after exposure to asbestos before obvious symptoms appear and a definitive diagnosis is made. While there still is no cure - and the prognosis is typically poor - significant progress has been made in recent years regarding treatment options and various alternative therapies.
How Asbestos Causes Mesothelioma
Mesothelioma cancer develops after exposure to asbestos, which most often occurs in the workplace –in industrial settings, shipyards, auto repair shops, old houses, schools and public buildings. It takes long-term exposure to make someone at risk, but heavy, short-term asbestos exposure has been known to cause mesothelioma cancer.
Microscopic asbestos fibers are breathed in or swallowed. The human body has difficulty destroying or getting rid of these fibers. Over decades, the fibers cause biological changes that result in inflammation, scarring and genetic damage. The most susceptible area to these fibers is the lining of the lungs, called the pleura, although fibers also can become trapped in the lining of the abdominal cavity (peritoneum). Once fibers cause biological damage, the stage is set for a 20- to 50-year latency period for mesothelioma to develop.
Types and Symptoms
Pleural
develops in thelining of the lungs
- coughing
- chest pain
- difficulty swallowing
- fatigue
- night sweats & fever
- shortness of breath
Pericardial
develops in thelining of the heart
- coughing
- chest pain
- difficulty swallowing
- fatigue
- irregular heartbeat
- night sweats & fever
Peritoneal
develops in thelining of the abdomen
- fatigue
- weight loss
- abdominal pain
- abdominal swelling
- nausea and vomiting
- constipation or diarrhea
Pleural mesothelioma is the most common type of mesothelioma, representing about 75 percent of cases. Peritoneal mesothelioma is the second most common type, consisting of about 10 to 20 percent of cases. Approximately 1 percent of cases are of the pericardial variety. Another rare type known as testicular mesothelioma represents less than 1 percent of cases.
How Mesothelioma is Diagnosed
All patients have a unique path to a diagnosis, but the most important factors to an accurate diagnosis are imaging scans and biopsies. Doctors use several tests to diagnose mesothelioma. Most people initially undergo a basic chest X-ray to check for any abnormalities. If abnormal growth is detected, a doctor will recommend a more detailed imaging scan like a PET scan, CT scan or MRI. If mesothelioma is suspected, a biopsy will be recommended. In a biopsy, a tissue sample is collected to confirm the presence of mesothelioma cells.
Blood tests for mesothelioma are also available, but they do not confirm the presence of mesothelioma. Research and development is underway to determine if mesothelioma blood tests can aid in early diagnosis for at-risk former asbestos workers.
Staging
There are at least five systems that doctors use for the staging of pleural mesothelioma. Older systems like those created by Drs. Butchart and Sugarbaker did not classify tumors with tumor-node-metastasis (TNM) descriptors, so the International Mesothelioma Interest Group (IMIG) developed the detailed IMIG staging system in 1995. This system is the most widely used staging system for mesothelioma.
Possible Areas Affected in Each IMIG Mesothelioma Stage
- 1. Parietal Pleura
- 2. Visceral Pleura
- 3. Lung Tissue
- 4. Diaphragm
- 5. Mediastinum
- 6. Lining of Heart
- 7. Lymph Nodes (on affected side of chest)
- 8. Lymph Nodes (on opposite side of chest)