Mesothelioma | definition of mesothelioma by Medical dictionary

DefinitionMesothelioma is an uncommon disease that causes malignant cancer cells to form within the lining of the chest, abdomen, or around the heart. Its primary cause is believed to be exposure to asbestos.Description

Malignant mesothelioma is also known as asbestos cancer or simply “meso.” Mesothelioma causes cancerous cells to develop in the body’s mesothelium, where they can spread to and damage vital organs and tissue. These malignant cells can also metastasize to other regions of the body. Mesothelioma is very difficult to diagnose and responds poorly to most treatment modalities, accounting for a poor prognosis.

The disease derives its name from the mesothelium, a sac-like membrane that protects most of the body’s internal organs. It is divided into two distinct protective layers of cells: the visceral (the layer directly surrounding the organ) and the parietal (a sac around the body cavity). By releasing a lubricating fluid, the mesothelium allows the organs to move more freely within the body cavity; for example, the contraction and expansion of the lungs. The mesothelium is also referred to according to where it is located in the body: pleura (chest), peritoneum (abdomen), and pericardium (heart).

Peritoneal mesothelioma is the second most common form of the disease, accounting for less than 30% of all cases. Malignant cells form in the peritoneum, affecting the abdomen, bowel, liver, and spleen. Similar to pleural mesothelioma, the disease also causes a build up of excess fluid in the abdominal cavity. Normal bodily functions, such as digestion, can be hindered by the obstruction of organ movement.

Very rare forms of mesothelioma occur in the pericardium, as well as the mesothelium of the male and female reproductive organs. Cystic mesothelioma of the peritoneum, another rare form of the disease, occurs predominantly in women and is more benign in nature.

Malignant mesothelioma takes the form of one of three cell-types: epithelioid (50% to 70% of cases), sarcomatous (7% to 20% of cases), and biphasic/mixed (20% to 35% of cases). Of these cell-types, epithelioid mesothelioma carries the most favorable prognosis, followed by biphasic, and finally sarcomatous (very aggressive).

Mesothelioma remains relatively uncommon in the United States, with approximately 2,500 new cases reported annually. The incidence rates are much higher in Western Europe (over 5,000 cases reported annually). These numbers are expended to climb dramatically over the next 20 years. Older males (median age 60 at diagnosis) are three to five times more likely to develop mesothelioma than women. This is most like do to male predominance in those professions with an increased risk of asbestos exposure.

Approximately 80% of all mesothelioma patients have a history of asbestos exposure. The majority of these patients were employed in an industry that involved the use of asbestos in some fashion. In addition to occupational exposure, household exposure of family members is not uncommon. An exposed individual can carry the asbestos particles on their clothing, skin, and in their hair when they return home, resulting in paraoccupational exposure. Even brief exposure to asbestos, as little as one to two months, can result in long-term consequences. Although the dangers of asbestos have been known for decades, the long latency period of mesothelioma (30 to 40 years) means that majority of patients were already exposed as far back as the 1950s. It is estimated that up to eight million Americans have already been exposed. Several industries, in particular, show a higher incidence of asbestos exposure:

Patients suffering from peritoneal mesothelioma most commonly exhibit signs of pain and/or swelling in the abdomen from fluid retention or tumor growth. Weight loss, nausea, bowel obstruction, anemia, fever, and swelling in the legs and/or feet are also known symptoms.

Once a confirmation of malignant mesothelioma has been established, the doctor will conduct further tests to determine the extent to which the primary disease has spread. This diagnostic process is known as “staging.” Malignant pleural mesothelioma of can be broken into four stages:

Recurrent malignant mesothelioma may also occur, where the cancer returns in its original location or elsewhere in the body even after treatment.

Surgery, the most common treatment, involves the removal of the tumor. In the early stages of mesothelioma, this only involves removal of a section of the mesothelium and surrounding tissue, but may require removing part of the diaphragm as well. For more advanced stages of the disease, removing the entire lung may be the only option, which is known as pneumonectomy.

Radiation therapy, also known as radiotherapy, destroys and shrinks the cancer cells through various types of radiation. Both external (such as a machine) and internal (such as radioisotopes) radiation therapies can be utilized effectively to treat malignant mesothelioma.

Pain and other symptoms caused by fluid build-up around the chest and/or abdomen can be treated by drain excess fluid through a needle or tube. These procedures are known as thoracentesis (chest) and paracentesis (abdomen). Drugs, radiotherapy, and surgery can also relieve or prevent further fluid accumulation.

The stage and location, what cell-type is involved, as well as the patient’s age and histology factor greatly on life expectancy. Unfortunately, even with aggressive treatment, the prognosis for mesothelioma patients is poor. Pleural mesothelioma offers a median survival time of approximately 16 to 17 months after initial symptoms. Prognosis for peritoneal mesothelioma is poorer and has a median survival time of only ten months after initial symptoms. Unfortunately, the more advanced stages of mesothelioma may offer as little as four or five month’s survival time.

The survival time for patients with localized mesothelioma can be extended several months with aggressive therapy, with roughly 20% of patients surviving past the five-year mark. Therapy programs recently developed at leading cancer centers have extended this survival time even further. Dr. Sugarbaker, of the Brigham and Women’s Center in Boston, has achieved a median of 40% survival rate at five years with his treatment regimen for pleural mesothelioma, as reported in the Journal of Thoracic and Cardiovascular Surgery. Other programs are also exhibiting favorable results. However, despite such successes, no cure for mesothelioma currently exists.

Jaurand, Marie-Claude, and Jean Bignon (eds). The Mesothelial Cell and Mesothelioma. New York: Marcel Dekker, 1994.

Robinson, Bruce, and A. Philippe Chahinian (eds). Mesothelioma. London: Martin Dunitz, 2002.

Pistolesi, Massimo, and James Rusthoven. “Malignant Pleural Mesothelioma.” Chest 126 (October, 2004): 1318-1329

Sugarbaker, David, et al. “Resection Margins, Extrapleural Nodal Status, and Cell Type Determine Postoperative Long-Term Survival in Trimodality Therapy of Malignant Pleural Mesothelioma.” Journal of Thoracic and Cardiovascular Surgery 117 (January, 1999): 54-65

van Ruth, Serge, Paul Baas, and Frans Zoetmulder. “Surgical Treatment of Malignant Pleural Mesothelioma.” Chest 123 (February, 2003): 551-561

Mesothelioma Research Foundation of America. 5716 Corsa Ave., Suite 203, Westlake Village, CA 91362. (800) 281-9804. http://www.mesothelioma-rfa.org.

The Mesothelioma Center. 1030 Fifth Ave., Pittsburgh, PA 15219. (412) 471-3980. http://mesotheliomacenter.org.

“Malignant Mesothelioma.” National Cancer Institute http://www.nci.nih.gov/cancertopics/types/malignantmesothelioma/.

“Mesothelioma.” Mesothelioma Information http://www.mesoinfo.com.

“Mesothelioma.” Mesothelioma Web http://www.mesotheliomaweb.org.

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Mesothelioma | definition of mesothelioma by Medical dictionary

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