Mesothelioma is a disease where cells in the mesothelium become abnormal and divide without order or control. The cancer cells can invade nearby tissues and organs or spread to other areas of the body. Mesothelioma usually affects the pleura, the membrane that surrounds the lungs. This form of the disease is called pleural mesothelioma. The peritoneum can also be affected, which is known as peritoneal mesothelioma. It rarely begins in the pericardium.
Decades ago, researchers connected the development of mesothelioma to crocidolite asbestos exposure in South African miners. Approximately 70% to 90% of patients who develop mesothelioma have some prior asbestos exposure commonly through work. Mesothelioma cases tend to come from those working near or in shipyards and plants, steel mills, and factories that contained asbestos products.
In the United States, approximately 2,000 to 3,000 cases of mesothelioma are diagnosed annually. Men are more likely to be diagnosed with mesothelioma than women, although the gap is closing. Before regulations concerning asbestos were established, workers carried home asbestos fibers on their clothing, exposing their family members as well. The risk of developing mesothelioma increases with age as well as the increased duration and intensity of exposure to asbestos.
What Causes Mesothelioma?
People who have been exposed to asbestos are the most likely to develop mesothelioma. Approximately 70% to 80% of mesothelioma patients have worked with asbestos. However, some patients have had no known exposure.
Tobacco usage alone does not increase the risk of developing mesothelioma. However, smokers who are exposed to asbestos have an increased risk of lung cancer.
Is Mesothelioma Common?
Mesothelioma is a relatively rare form of cancer. While other cancer diagnoses have increased considerably over the past quarter-century (over 1/4 of the U.S. population will suffer from some type of cancer in their lifetime), mesothelioma is still not common. Around 3,000 new cases are reported in the U.S. every year, with most patients being older men. However, women are also known to suffer from mesothelioma, which can occur at any age.
People working in construction, building, demolition, or in the making of heating products have an increased risk of developing mesothelioma.
What are Common Symptoms of Mesothelioma?
Mesothelioma symptoms typically do not develop until decades after initial asbestos exposure. Additionally, many mesothelioma symptoms are similar to less serious conditions. However, if you experience any of the symptoms listed below, see a doctor immediately:
- Shortness of breath
- Unusual weight loss
- Chest pain, especially after exertion
- Bowel obstruction
- Abdominal pain
- Anemia (unusual fatigue and listlessness)
- Abnormal blood clotting or excessive bleeding
If it has spread, you may also feel neck or facial pain and have trouble swallowing.
Diagnosing mesothelioma can be difficult. Typically, a doctor will conduct a complete physical exam, which will include x-rays of the abdomen and chest and a respiratory function test. X-rays may be replaced with advanced techniques such as an MRI or CAT scan.
If the doctor has concerns, he or she will refer you to a cancer specialist, also known as an oncologist. The cancer specialist will perform a biopsy by taking a tissue sample from your abdomen or chest. This sample will be examined under a microscope. If the pathologist finds mesothelioma, the oncologist will need to establish whether the disease is localized or has spread.
Types of Mesothelioma
There are four main types of mesothelioma: pleural, pericardial, peritoneal, and testicular. Each of these types is determined by where in the body the cancer first develops.
Pleural mesothelioma is a malignant cancer of the lungs, specifically the pleura, or the lining of the chest cavity and lungs. This cancer is particularly aggressive, and accounts for the majority of all mesothelioma cases diagnosed. The prolonged inhalation of asbestos contributes to the vast majority of these cases developing. With 2,500 to 3,000 new cases diagnosed in the United States each year, pleural mesothelioma makes up approximately 75-80% of all diagnosed cases.
When the pleura is affected by this cancer, it becomes thickened, which results in the chest cavity and lungs being unable to fully expand and contract. This creates a buildup of fluids in the chest over time. When pleural mesothelioma is detected, it usually occurs during a chest x-ray, which shows the fluid buildup in the chest cavity. A patient may present with chest pain, a dry cough, and shortness of breath. Since these symptoms are also shared by many other conditions, it's imperative to communicate about any asbestos exposure and discuss receiving a thorough examination with your physician.
Pericardial Mesothelioma is a cancer that affects the pericardium, or the tissues that line the heart. This type of mesothelioma is exceedingly rare, representing only 1% of all mesothelioma cases.
Since this type of cancer is so rare, doctors are still researching it to determine the cause. It may or may not be related to asbestos exposure, but the symptoms can be similar to those of pleural mesothelioma. In addition, due to its rarity, pericardial mesothelioma has a poor prognosis. Patients survive an average of 6-12 months, and care is primarily aimed at reducing discomfort and symptoms.
Peritoneal mesothelioma develops in the peritoneum, or the thin lining of the abdominal cavity and its internal organs. This type of mesothelioma is the second-most common occurrence, at 15-20% of all mesothelioma cases. This type of cancer can occur when asbestos that are inhaled make their way down to the abdominal area over time via the lymphatic system. It may also occur when asbestos are ingested; as the fibers are so tiny it may be possible to ingest them without knowing it. Early on, a patient may experience unexplained weight loss, stomach pain, nausea, vomiting, high fevers, or seizures.
This type of mesothelioma has a more positive prognosis than the other types, with a longer life expectancy possible when detected early on and treated with surgery in conjunction with other, complementary treatments.
Testicular mesothelioma is a cancer that develops in the lining surrounding the testicles, occuring in men between the ages of 55-75. By far, this is the rarest of all four types of mesothelioma. Accounting for less than 1% of all cases, testicular mesothelioma has only been reported in about one hundred cases. Due to its extreme rarity, it is difficult to determine a full range of symptoms for this type of mesothelioma. According to the limited medical literature available, a patient may present with a painless mass on the scrotum, or possible swelling or pain of the testicles caused by fluid buildup. Typically, it will develop in one testicle before spreading to another.
If caught early on and removed, the prognosis for this type of mesothelioma is more favorable than other types, despite the relative lack of a standard treatment. However, testicular mesothelioma also comes with a high recurrence rate; around 93% of patients experienced a recurrence of the cancer five years after their first diagnosis.
What is Mesothelium?
The mesothelium is a membrane covering and protecting most of the body's internal organs. The mesothelium contains two layers of cells, with one surrounding the organ and the other forming a sac around it. The mesothelium creates a lubricating fluid which is released between these layers allowing moving organs, such as the lungs and heart, to glide easily against nearby structures. The mesothelium has different names, depending on its location in the body:
- The peritoneum is the mesothelial tissue that covers most organs in the abdominal cavity
- The pleura is the membrane surrounding the lungs and lining the wall of the chest cavity
- The pericardium covers and protects the heart
- The mesothelial tissue surrounding the male internal reproductive organs is called the tunica vaginalis testis
- The tunica serosa uteri cover the internal reproductive organs in women
What Treatment is Available for Mesothelioma?
Treatment of mesothelioma depends on the stage of the disease. Surgery is normally performed if the cancer is localized. The oncologist, or cancer specialist, will extract the affected part of the chest lining and nearby tissue. If the pleura is affected, a lung and part of the diaphragm may need to be removed. Radiation therapy can also be used. This procedure uses targeted ionizing radiation to kill malignant cells. If the cancer has spread, a doctor will most likely use chemotherapy, which utilizes anti-cancer medications. To relieve pain and other symptoms, a doctor will insert a tube to drain fluid from the abdomen or chest.
Does Asbestos Cause Mesothelioma?
The primary cause of mesothelioma is exposure to asbestos. There are several types of asbestos, but asbestos can broadly be described as a fibrous mineral that has been used in numerous industrial products.
When workers use products containing asbestos, they may be exposed to asbestos dust. Workers can breathe airborne asbestos fibers, which then become lodged in the lungs. These tiny fibers can work their way through the lungs and into the membrane surrounding the lungs. The asbestos fibers can irritate the mesothelium or peritoneum, eventually causing cancerous cells to develop.
The particles can reach the smallest and most distant parts of the lungs. These fibers cannot be removed by coughing unless they attach to mucus in the air passages. They can also remain in the tissue around the chest or stomach cavity, where they cause inflammation and lead to mesothelioma.
Asbestos particles can damage the lungs by forming scar tissue. Those who have been exposed to asbestos have a seven times greater risk for developing lung cancer than those who have not been exposed. The three causes of death for those with significant asbestos exposure are mesothelioma, lung cancer, and lung scarring (aka asbestosis).
Current Mesothelioma Research
The National Cancer Institute (NCI) currently sponsors clinical trials that attempt to find new treatments and improve existing ones. If you want to participate, consult with your doctor and call 1-800-4CANCER. For more information, visit cancer.gov to locate news on clinical trials and a catalog of relevant publications.