Mesothelioma Questions

Mesothelioma is a rare cancer that occurs in the thin layer of tissue, known as the mesothelium, which lines and protects the major organs of the body such as the heart, stomach and lungs. This form of cancer is the result of repeated and unprotected exposure to asbestos. The symptoms and the latency period of this disease make it difficult to diagnose. In general, mesothelioma responds poorly to the treatments currently being used.

Those most at risk in developing mesothelioma are people that have worked with asbestos over a period of 25 to 50 years. Due to the lack of protection and regulations during those years, these workers were constantly exposed to the dust and fibers from asbestos, which eventually caused the cells of the mesothelium to become abnormal.
Others at risk include family members who have had prolonged contact with asbestos workers because they carry the toxic material on their clothes, skin and hair.

Mesothelioma is a rare type of cancer.  It begins in the cells of the outer lining of organs, called the mesothelium.  It most commonly affects the lung, but may also affect the heart and abdominal organs.  Pleural mesothelioma enlarges until it limits lung movement and can then spread to the mediastinum.  Death commonly occurs in 4 months to 1 year with less than 10% living more than 3 years after diagnosis is confirmed.
Mesothelioma is most often occurs after asbestos exposure.  This exposure can be 20 to 40 years prior to tumor formation. Smoking and asbestos exposure together greatly increases the risk.  The families of workers who are exposed to asbestos can also be at risk due to inhalation of fibers that are on a worker’s clothes.  Most asbestos exposures happened in the past so the surge of mesothelioma cases is expected to decline in the years to come.

Mesothelioma is a very rare cancer which originates in the membranes lining the chest, abdominal cavities or the heart.  These membranes are called mesothelium, which is a protective sac of thin tissues covering vital organs.  The mesothelium is comprised of two layers, the visceral membrane which covers the organ and the parietal membrane which forms a sac around it.  A fluid is produced by the mesothelium to allow organs to move easily in the body.

Mesothelioma occurs when the cells in the tissue continually produce this fluid. Excess fluid and tissue builds up around these vital organs making it difficult for them to function effectively.  The cells can then multiply and spread to other organs or areas in the body which is called metastasis.

The majority of malignant mesotheliomas (around 90%) occur in the lining of the lungs.  The remaining cases of mesotheliomas develop in the abdomen and the heart.

The three forms of mesothelioma are pleural, peritoneal, and pericardial.

Pleural mesothelioma affects the lung cavity and the protective lining of the lungs.  Symptoms include shortness of breath, difficulty breathing or swallowing, persistent coughing and coughing up blood, shortness of breath, rasping, weight loss, and fever.

Peritoneal mesothelioma affects the stomach and abdomen initially; however it can spread to other parts of the body.  Symptoms include abdominal pain and swelling, nausea, appetite loss, vomiting, chest pain, breathing problems, obstructed bowels, fever, bleeding, and abnormal blood clotting.

Pericardial mesothelioma affects the heart and the surrounding cavity.  Symptoms include chest pain, heart palpitations, persistent coughing, shortness of breath, and general breathing trouble.

Certain organs such as the heart, the lungs, and the abdomen are surrounded by a thin tissue membrane.  The pericardium is the membrane that surrounds the heart, the pleura surrounds the lungs, and the peritoneum surrounds the abdomen.  These membranous layers are comprised of cells called mesothelium.

Cells within the body constantly divide and grow.  An irregular or abnormal growth or division of the cells creates a marked mass (tumor).  A tumor that develops in the mesothelium is called mesothelioma, or cancer of the mesothelium.

The most common type of mesothelioma is Malignant Pleural Mesothelioma (MPM).  The rarest form of mesothelioma is pericardial mesothelioma.  Mesothelioma is also referred celothelioma and/or asbestos cancer.  (It is important to note that Asbestosis is not the same as Mesothelioma.  Asbestosis is a non-malignant, chronic lung disease.)

Word Roots:
meso = middle or median
thelium  = layer of cellular tissue

Mesothelioma is a rare form of cancer caused by exposure to asbestos. It attacks the lining of the lungs (the pleura), the lining of the sac surrounding the heart (the pericardium), or the lining of the abdominal cavity (the peritoneum).

There are three cancer cell types in mesothelioma: epithelioid, sarcomatous, and mixed, which includes both epithelioid and sarcomatous cells. These are abnormal cells which multiply and cause fluid build-up, thickening, or tumors, and therefore impede the normal structure and function of the heart, lungs, or abdominal organs.

Symptoms of pleural mesothelioma may include shortness of breath, pain, or cough, as a result of fluid build up in the pleural space. On auscultation, normal breath sounds are diminished. Peritoneal mesothelioma can present as swelling or distention (increased girth related to ascites), or pain related to a mass. Symptoms of both are often non-specific in the early stages.

Mesothelioma is benign or malignant sarcomas that arise from the mesothelial lining that covers the serous membranes of the pleura, peritoneum and pericardium.  The incidence of mesotheliomas occurring in the pleura is highest accounting for 80%.   The occurrence for mesotheliomas in the peritoneum is 5%.  The rarest occurrence is in the pericardium with only 0.4 % being the primary sight.  Mesotheliomas are related to past occupational asbestos exposures.  The asbestos exposures may have been a short duration of 1 to 2 years occurring 20 to 25 years in the past with a peak incidence of 35 to 40 years.  Mesotheliomas present in the fifth to seventieth decades of life.  Males are 3 to 5 times more likely to present with mesotheliomas then are females.  There is no racial predilection of disease development.   The mortality rate is less than 5% for 5 years.

•    Mesotheliomas are primary tumors arising from the surface lining of the pleura, peritoneum, or pericardium.  Pleural mesotheliomas are the most common form, comprising about 80% of the new cases.
•    There are between 2,000 to 3,000 new cases of mesothelioma diagnosed in the United States every year and the incidence is increasing. The peak incidence of mesothelioma is expected to occur in this country in the year 2020.
•    Men outnumber women by a 3:1 ratio.
•    The mean age at onset of symptoms is about 60 years.
•    The latent period between exposure and onset of symptoms ranges from 20 to 40 years.
•    The Environmental Protection Agency banned all new uses of asbestos in 1989.  However, uses established prior to 1989 are still allowed.  Asbestos continues to be imported and used in the United States.

Mesothelioma is a type of cancer of the mesothelial cells in the membranes that line an organ. The most common area of mesothelioma is in the pleura (surrounding the lungs) but can include the peritoneum (surrounds organs in the abdomen). The most common cause associated with mesothelioma is asbestos exposure. Asbestos usage has decreased in the last fifteen to twenty years due to its link with causing malignancy. Asbestos is a generic term for a group of mineral silicates. Asbestos has great insulation properties but its fibers are easily spread through airborne. Asbestos was most commonly used in insulation products, which was directly used by some construction workers, factory workers, and miners. The risk of mesothelioma increases with increased exposure. Mesothelioma symptoms tend to show until twenty to fifty years following exposure. Though tobacco use can also be a cause of mesothelioma, it is has a stronger link to causing lung cancer.

The cells that normally line the pleura and peritoneum are called mesothelial cells.  Primary tumors that arise from mesothelial cells are mesotheliomas.  Eighty percent of mesotheliomas arise from the pleura; the other twenty percent of mesotheliomas arise from the peritoneum.

Seventy-five to ninety percent of mesotheliomas are malignant.  The majority of mesotheliomas are described as malignant pleural mesotheliomas.

The majority of mesotheliomas are caused by asbestos.  Asbestos are naturally occurring, heat-resistant fibrous silicates.  The fibers of asbestos can be long and thin and maybe curved or straight.  The straight fibers of asbestos are called amphiboles.  There are five different types of amphiboles, however the type associated with mesothelioma is crocidolite.

Another cause of mesothelioma is thorium dioxide which is used in therapeutic radiation.  Mesotheliomas are also thought to be caused by zeolite (a silicate found in soil).