What Is Mesothelioma?

What Is Mesothelioma can be answered in brief as a virulent form of cancer that attacks the thin layer of cells, called the mesothelium, that line the body’s organ cavities. Seventy to 80 percent of all diagnosed cases are due to asbestos exposure in the workplace, although symptoms may take as long as 50 years after the initial exposure to appear. Not all of it is related to asbestos exposure. Other causative agents may include simian virus 40, a component of polio vaccine; Thorotrast, a compound once used in x-rays; and erionite, a mineral material with a chemical structure similar to that of asbestos.

It is diagnosed in approximately 2,000 to 3,000 new patients in the United States each year, and takes the lives of 20,000 patients annually around the world. The rate of diagnosis is expected to increase and peak before declining in the coming decades, however, due to the era of peak use of asbestos combined with the latency period associated with mesothelioma.

Mesothelioma has a poor prognosis, in great part because the disease often remains undiagnosed until it has advanced to Stage III or Stage IV. The five-year survival rate for mesothelioma patients was 10 percent in 2006, according to the American Cancer Society. However, some patients, in whom the disease was caught early, have reported long remissions after surgical intervention, highlighting the importance of early detection. Anybody with a history of asbestos exposure would be well advised to see their physician regularly, and to take symptoms like a lingering cough very seriously.

Types of Mesothelioma

The three most common sites where mesothelioma develops are the pleura (the outer lining of the lungs and chest wall,) the peritoneum (the lining of the abdominal cavity and outer lining of the stomach,) and the pericardium (the sac surrounding the heart and lining the inner chest cavity.)

Because patients are frequently already in the latter stages of the disease when first diagnosed, metastasis is common at the time of diagnosis. Metastasis shows a localized pattern of spread, generally affecting organs and tissues near the site of the original tumor. Mesothelioma can also develop in a non-malignant form.

Malignant diagnosis is complicated by the fact that symptoms frequently are not specific to the disease itself, but rather can be secondary effects of any number of underlying pathologies affecting the area of the body where the disease manifests. Patient history is therefore the number one criteria in suspecting the presence of the disease.

Pleural type presents with many of the same symptoms that accompany any pleural effusion, including shortness of breath, dry cough, and a sharp pain upon inhalation, either in the rib cage or the small of the back. Other symptoms may include fatigue upon minimal exertion, difficulty swallowing, night sweats or fever, or swelling in the extremities.

Symptoms of Mesothelioma

The symptoms of peritoneal mesothelioma may include abdominal pain or distension secondary to a build-up of fluid in the abdominal cavity (ascites,) bowel obstruction, weight loss, fatigue and abdominal pain.

The symptoms of pericardial mesothelioma are related to the build-up of fluid in the pericardial sac and may include dry cough, shortness of breath, chest pain and heart palpitations.

If patient history gives the examining physician any reason to suspect mesothelioma, the physician will order imaging studies to confirm or rule out the diagnosis. In cases of pleural mesothelioma, chest x-rays will show thickening of the pleura; since this is a common finding in many types of lung disease, follow-up tests such as CT scans, MRI scans or PET scans will likely be necessary. In cases of peritoneal mesothelioma, initial diagnosis will also rely upon imaging studies as well as a procedure called peritoneoscopy, in which a tube is inserted into the abdomen that allows a physician to look for abnormal tissue. Pericardial mesothelioma is perhaps the hardest of the three to diagnose, because of the nonspecificity of its symptoms.

In all three instances the diagnosis will be confirmed through biopsy – either a needle biopsy or an excision biopsy. Once a sample of the tumor is removed, a pathologist will examine the cells under a microscope to confirm the mesothelioma diagnosis, and to determine the stage of the disease.

Mesothelioma Staging

Like other forms of cancer, mesothelioma progression is generally divided into four stages. Although there are three staging systems commonly used by oncologists specializing in mesothelioma, the criteria are roughly the same:

  • Stage I: Mesothelioma may be found unilaterally on either the right or left side of the chest with some diaphragmatic involvement;
  • Stage II: Mesothelioma is found bilaterally on both sides of the pleura, and has moved into the heart, stomach, or esophagus. Lymph nodes may also be affected;
  • Stage III: Mesothelioma has spread into the abdominal cavity;
  • Stage IV: Mesothelioma has reached other organ systems and has entered the bloodstream.
Treatments for Mesothelioma

Surgery to remove the mesothelioma tumor is rarely attempted, simply because of the advanced stage at which most cases are diagnosed, as well as the close proximity of the cancer to vital organs. Surgical options which may be considered in cases of Stage I diagnoses include pleurectomy (removal of the pleura) and extrapleural pneumonectomy (removal of the entire lung as well as some other nearby tissues). Extrapleural pneumonectomy in combination with specific chemotherapy drugs has been found to increase the five-year survival rate significantly.

Mesothelioma is more commonly treated with radiation and chemotherapy. Since mesothelioma is considered incurable, these are often considered palliative treatments that help improve the quality of a patient’s remaining months or years of life, by shrinking the tumor that causes many of the symptoms.

Minor surgical procedures like thoracentesis, paracentesis and pericardiocentesis also offer a measure of palliative relief by removing the fluid that has built up respectively in the pleural cavity, the abdomen or the sac around the heart.

The median survival time for a patient with pleural mesothelioma is only six to 18 months, depending on the stage of the cancer. Pericardial and peritoneal varieties of the disease have even shorter survival times.