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Types of Mesothelioma (for Pleural)

Mesothelioma is an uncommon form of cancer that affects the mesothelium, a protective membrane that surrounds vital organs. There are three primary types of mesothelioma: pleural, peritoneal and pericardial. Doctors distinguish the types several ways, most commonly by the cancer's original location.

The mesothelium of the chest is known as the pleura. Pleural mesothelioma, the most common of the three types, starts in the lining of the lungs. The mesothelium that lines the abdominal cavity is known as the peritoneum. Peritoneal mesothelioma originates in the abdomen's lining. The protective layer surrounding the heart is called the pericardium, and pericardial mesothelioma begins in the lining around the heart.

Although these disease types share qualities, they do have important differences. The location of the cancer can directly influence symptoms that patients experience, available treatment options as well as life expectancy.

Mesothelial cells secrete a lubricating fluid that helps prevent friction as organs move, such as in the lungs during breathing. When mesothelial cells become cancerous, typically through exposure to asbestos, they divide uncontrollably and form aggressive tumors that are likely to spread to other parts of the body. If you are interested in learning more, PleuralMesothelioma.com offers a comprehensive informational packet created to inform mesothelioma patients and their families. Fill out this form to get a packet mailed to you overnight.

Pleural Mesothelioma

Pleural mesothelioma accounts for about 75 percent of all mesothelioma cases. A cancer of the pleura, not the lungs themselves, pleural mesothelioma thickens the lungs' protective lining and can result in a series of respiratory problems. Common symptoms include:

• Chest or lower back pain
• Shortness of breath
• Difficulty swallowing
• Cough
• Hoarseness
• Fever
• Fatigue
• Weight loss

Because early symptoms also can be caused by medical conditions that are more common and far less serious, pleural mesothelioma is often difficult for doctors to diagnose. Further, the time span between initial exposure to asbestos and a mesothelioma diagnosis can take between 35 and 40 years.

Early detection is crucial to successful treatment because the stage of a tumor has a significant impact on a patient's outlook. If tumors are found before they have a chance to spread, surgery is an option. If possible, doctors prefer a multimodal approach to treatment, which combines surgery, chemotherapy and radiation therapy. However, most treatments are palliative, meaning they can relieve symptoms and improve a patient's quality of life but do little to extend the life.

Peritoneal Mesothelioma

Peritoneal mesothelioma develops in the protective layer that surrounds the abdomen (stomach). It is far less common than pleural mesothelioma, affecting approximately 20 percent of all mesothelioma patients. Scientists believe tumors of the peritoneum occur when asbestos enters the stomach, either through ingestion or the accidental swallowing of inhaled fibers after coughing. Heavier exposure to asbestos has caused a steady increase in peritoneal mesothelioma cases over the past 30 years.
According to the American Cancer Society, stomach pain is typically the first noticeable symptom of peritoneal mesothelioma. Other common symptoms patients experience include:

• Weight loss
• Nausea and vomiting
• Abdominal swelling
• Constipation
• Fatigue

These symptoms are a result of fluid buildup in the abdomen. Just as in pleural mesothelioma, symptoms are vague, and their underlying cause is difficult for doctors to separate from more common diseases. Peritoneal mesothelioma is highly aggressive, and a positive prognosis depends on early detection before the cancer has a chance to spread.    
Although a few cases of long-term survivors are documented, the rarity of peritoneal mesothelioma makes it a particularly fatal disease. By the time tumors typically are discovered, they are too advanced to be surgically removed. When possible, doctors recommend multimodal treatment combining surgery and chemotherapy to help relieve symptoms.
Recent medical advances have led to improved treatment methods like injecting heated anti-cancer drugs directly into the abdomen. This experimental type of chemotherapy – called heated chemotherapy – hikes the survival rate of some peritoneal mesothelioma patients.  

Pericardial Mesothelioma

Pericardial Mesothelioma is the rarest type of mesothelioma cancer. It affects the protective layer of tissue surrounding the heart and accounts for only 1 percent of all mesothelioma cancers. There are only about 200 known cases of pericardial mesothelioma documented worldwide.
Asbestos exposure is documented in several patients with pericardial mesothelioma, but doctors have yet to determine how toxic fibers get to the pericardium. Once asbestos fibers reach the heart, they penetrate the surrounding mesothelial tissue, which results in inflammation, scarring and fluid buildup. Pericardial mesothelioma is particularly fatal because excess fluid prevents the heart from fully expanding, thus dangerously reducing blood flow.
Symptoms for pericardial mesothelioma often resemble those of other heart conditions. In addition to sharp chest pains, other common symptoms include:

• Difficulty breathing
• Irregular heartbeat
• Fever
• Weight loss
• Fatigue

Symptoms occur when the tumor puts pressure on the heart or causes excess fluid to surround the pericardium and limit heart function. Diagnosing pericardial mesothelioma can be difficult because common detection methods – X-rays and ultrasounds, for example – lack the sensitivity to detect the cancer's unique growth pattern.
Unless this mesothelioma is discovered in its earliest stages, surgery is typically not an option because of the numerous risks involved with operating so close the heart. In most cases, chemotherapy and radiation therapy are ineffective, so doctors prefer palliative treatments such as removing fluid to relieve symptoms.  

Testicular Mesothelioma

Testicular mesothelioma is a highly aggressive cancer that affects the mesothelial lining of the testes, also known as the tunica vaginalis. Because it is the rarest form of the disease, testicular mesothelioma is often difficult for doctors to diagnose. Since 1957, there have only been about 100 reported cases which accounts for less than 1 percent of all mesotheliomas. In most cases, testicular mesotheliomas are secondary tumors that have spread from the peritoneum to the testes.
Researchers have yet to determine a complete list of symptoms, but the main indicators of testicular mesothelioma include lumps on the testicles and swelling of the scrotum. Treatment typically includes partial or complete removal of the testes followed by chemotherapy and radiation therapy to kill cancer cells and prevent future spreading.

Mesothelioma Cell Types

In addition to classifying mesothelioma cancers by initial location, doctors also distinguish among types based on how they appear under a microscope. The anatomical study of cells and tissue, or histology, has identified three primary mesothelioma cell types: epithelial, sarcomatoid and biphasic. Epithelial mesothelioma is the most common variety, occurring in 50 to 70 percent of malignant mesothelioma cases. These cells are uniform and tube-like in appearance. Of all histological types, epithelial cells respond best to treatment.

Sarcomatoid mesothelioma is far less common, only occurring in 7 to 20 percent of cases. Under a microscope, these cells usually overlap and are long, irregular and spindle-shaped. The outlook for patients with sarcomatoid mesothelioma is relatively poor because this cancer type is aggressive and resistant to treatment.

Biphasic or "mixed" mesothelioma features a combination of epithelial and sarcomatoid cells. When mixed, these cells are usually distributed in different parts of the tumor rather than evenly throughout. It is the second most common cell type with approximately 20 to 35 percent of all mesotheliomas classified as biphasic. The outlook for biphasic mesothelioma varies depending on the ratio of epithelial to sarcomatoid cells. Since sarcomatoid cells do not respond well to treatment, mixed mesotheliomas with a greater amount of epithelial cells generally have a more positive patient outlook.

Sources

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