Types

What are the different types of mesothelioma?

Pleural Mesothelioma – affects the chest and lungs

Malignant pleural mesothelioma often originates within the chest cavity and can, at times, involve the lung. This particular form of mesothelioma can metastasize to numerous organs in the body – even the brain - and tends to do so more frequently than not.

Pleural mesothelioma is not always easily detectable. Frequently, in the early stages of the disease, symptoms may be mild. Patients usually report pain in one area of the chest that never seems to go away, weight loss and fever. Occasionally, other symptoms are more severe and include problems with breathing due to fluid build up in the chest. A CT Scan of the chest area has proven to be the best test for identifying how far along the disease has progressed.

Frequently serum markers are used to diagnose of various forms of cancer. Mesothelioma cannot be diagnosed using this method as no serum markers currently exist. If high levels of hyaluronic acid are present it may be possible to distinguish mesothelioma from other types of cancer or to determine the effectiveness of a treatment protocol.

The survival rate for patients diagnosed with pleural mesothelioma typically is not high. Patients typically do not live beyond seventeen months from the onset of symptoms. Only 8% of those diagnosed with mesothelioma will live three to five years from the onset of symptoms.

Pericardial Mesothelioma – affects the heart

Pericardial mesothelioma is the least common form of mesothelioma. Pericardial mesothelioma, as the name suggests, involves the heart. This rare type of mesothelioma invades the pericardium, the sac that surrounds the heart. As the cancer progresses, the heart is not able to deliver oxygen as efficiently to the body causing further decline in health at an increasingly rapid rate. The symptoms most commonly associated with pericardial mesothelioma mimic those of a heart attack: nausea, pain in the chest and shortness of breath.

Peritoneal Mesothelioma – affects the abdomen

Peritoneal mesothelioma originates in the abdomen and will frequently spread to other organs in area including the liver, spleen or bowel. Severe abdominal pain is the most common complaint that patients present to their doctor. There may also be a discomfort level with fluid build up in the abdomen as well. Other symptoms of peritoneal mesothelioma may include difficult bowel movements, nausea and vomiting, fever and swollen feet.

The survival rate is even worse for those diagnosed with peritoneal mesothelioma will patients typically surviving only ten months from time that they first started experiencing the symptoms noted above.

Malignant Mesothelioma

Malignant mesothelioma is an uncommon form of cancer and of all asbestos related diseases, the most serious. The symptoms associated with the disease make it difficult for doctors to diagnose. Often, by the time that a proper diagnosis is made, the disease has progressed to a point where patients do not respond well to treatment therapy. Malignant mesothelioma is caused almost exclusively by the inhalation of airborne asbestos particles. Another unique factor associated with the disease is that there can be a long latency period between the time an individual is exposed to asbestos and the actual manifestation of the disease in the form of malignant mesothelioma.

Benign Mesothelioma – affects the peritoneum

Cystic mesothelioma primarily affects women of younger age and affects the peritoneum. This type of mesothelioma is not frequently diagnosed and is also not a malignant form of the disease. It is, however, extremely difficult to identify and requires specialized microscopes and immunologic techniques to aid in diagnosis.

Mesothelioma in Uncommon Sites

A form of cardiac cancer that is rarely seen involves the pericardium. Tumors associated with this type of mesothelioma are not easily detectable and patients presented with this diagnosis tend to have a very low survival rate. There have also been reports of mesothelioma involving ovaries in women and the scrotum in men. Treatment for all of these rare forms of mesothelioma will vary depending on what stage a patient has progressed to but in most all cases the projected outcome is not favorable.

Glossary of Terms

asbestos: combination of several minerals that separate into long, threadlike fibers. Because they do not burn, do not conduct heat or electricity, and are very resistant to chemicals, these minerals are often used for making fireproof materials, electrical insulation, roofing, filters, etc. benign: doing no harm, good incidence: the frequency with which an event occurs (usually in a group at risk) pericardium: a thin membrane surrounding the heart and the roots of the great blood vessels.

peritoneum: a thin membrane that covers the abdominal cavity and partially covers some of the abdominal organs.

pleura: a thin membrane that covers the lungs (visceral pleura) and lines the chest cavity (parietal pleura) malignant: harmful, dangerous (a malignant tumor is a cancer).

median: middle number in a series of numbers (for example: median survival of 10 months means that for that specific group of patients the survival varied from probably 2 months to 30 months).

mesoderm: the middle layer of cells in an embryo, from which the muscular, skeletal, vascular, connective etc. tissues develop.

mesothelioma: a tumor of the mesothelium, that can be benign (localized) or malignant (diffusely spread), and that is most commonly caused by the ingestion of asbestos particles.

mesothelium: the thin layer of mesodermal epithelial cells that forms the pleura, peritoneum, pericardium.

metastases: the spread of tumor cells from one part of the body to another unrelated part of the body by the way of the bloodstream or lymphatics.

prognosis: prediction of the probable course of the disease in an individual. Prognostic factors are factors associated with prognosis.

TNM staging: assigning a stage to the tumor based on size, local versus disseminated growth, lymph node involvement and presence or absence of distant metastases.

tumor: a mass of tissue, a growth independent of its surrounding structures and having no physiological function/ a neoplasm. A tumor can be benign or malignant.

Symptoms

What are the warning signs of mesothelioma?

Mesothelioma is difficult to diagnose because the early signs and symptoms of the disease can be subtle at best. Symptoms are all too frequently ignored or dismissed by people who are inclined to attribute them to common every day ailments. Sometimes patients live with symptoms for up to 6 months before being diagnosed but usually the symptoms are present for two to three months prior to diagnosis.

About 60% of patients diagnosed with pleural mesothelioma experience lower back pain or side chest pain and there are frequent reports of shortness of breath. Lower numbers of people may experience difficulty swallowing, or have a persistent cough, fever, weight loss or fatigue. Symptoms to also consider are muscle weakness, loss of sensory capability, coughing up blood, facial and arm swelling and hoarseness.

Peritoneal mesothelioma originates in the abdomen and as a result, symptoms often include abdominal pain, weight loss, nausea, and vomiting. In the event that there is a hernia present, fluid build up may occur in the abdomen as well.

Anyone previously exposed to asbestos displaying any of these symptoms should seek medical attention right away.

Stages

How is mesothelioma staged?

Staging is the process of finding out how far the cancer has spread. Staging of mesothelioma is based on imaging studies such as x-rays, CT scans, and MRI scans. The treatment and outlook for patients with mesothelioma largely depends on the stage (extent of spread) of their cancer. Since pleural mesothelioma occurs most frequently and has been studied the most, it is the only mesothelioma for which a staging classification exists.

The staging system most often used for mesothelioma is the Butchart system. This system is based mainly on the extent of the primary tumor mass, and divides mesotheliomas into stages I through IV.

Butchart Staging System

• Stage I: Mesothelioma is present within the right or left pleura, and may also involve the lung, pericardium, or diaphragm (the muscle separating the chest from the abdomen) on the same side.
• Stage II: Mesothelioma invades the chest wall or involves the esophagus (food passage connecting the throat to the stomach), heart, or pleura on both sides. The lymph nodes in the chest may also be involved.
• Stage III: Mesothelioma has penetrated through the diaphragm into the peritoneum (lining of the abdominal cavity). Lymph nodes beyond those in the chest may also be involved.
• Stage IV: There is evidence of distant metastases (spread through the bloodstream to other organs).

Another staging system has recently been developed by the American Joint Committee on Cancer (AJCC). This is a TNM system, similar to staging systems used for most other cancers. T stands for tumor (its size and how far it has spread to nearby organs), N stands for spread to lymph nodes and M is for metastasis (spread to distant organs). In TNM staging, information about the tumor, lymph nodes, and metastasis is combined in a process called stage grouping to assign a stage described by Roman numerals from I to IV. Minor differences exist between the AJCC TNM staging system and the Butchart staging system.

TNM Staging System

• Stage I: Mesothelioma involves the right or left pleura. It may also have spread into the lung, pericardium, or diaphragm on the same side. It has not yet spread to the lymph nodes.
• Stage II: Mesothelioma has spread from the pleura on one side to the nearby peribronchial and/or hilar lymph nodes next to the lung on the same side. It may also have spread into the lung, pericardium, or diaphragm on the same side.
• Stage III: Mesothelioma has spread into the chest wall muscle, ribs, heart, esophagus, or other organs in the chest on the same side as the primary tumor, with or without spread to subcarinal and/or mediastinal lymph nodes on the same side as the main tumor. Subcarinal nodes are located at the point where the windpipe branches to the left and right lungs. Mediastinal lymph nodes are located in the space behind the chest bone in front of the heart. Mesotheliomas with the same extent of local spread as in stage II that have also spread to subcarinal and/or mediastinal lymph nodes on the same side are also included in stage III.
• Stage IV: Mesothelioma has spread into the lymph nodes in the chest on the side opposite that of the primary tumor, or directly extends to the pleura or lung on the opposite side, or directly extends into the peritoneum, or directly extends into organs in the abdominal cavity or neck. Any mesothelioma with evidence of distant metastases (spread to other organs through the bloodstream) or spread to organs beyond the chest or abdomen is included in this stage.

Although the recently developed TNM classification is the most detailed and precise, the original Butchart staging system is still used most often to describe the spread of pleural mesotheliomas. Understanding these staging systems for mesothelioma is important both for estimating and better understanding prognosis, and also for assessing therapeutic options.

Prognostic Factors

Because pleural mesothelioma has been better studied than peritoneal mesothelioma we know more about factors associated with prognosis for pleural mesothelioma. Younger age at diagnosis, performance status (functional status) and absence of weight loss are associated with a more favorable prognosis.

Mesotheliomas are usually of three different cell types (histological analysis): 1) epithelial cell type - has the most favorable prognosis; 2) fibrosarcomatous cell type - carries the worst prognosis and 3) mixed cell type - has an intermediate prognosis.

Risk Factors

What are the risk factors for malignant mesothelioma?

There are several risk factors that increase the likelihood that a person will develop mesothelioma. The primary risk factor is asbestos exposure. Exposure to this very harmful substance can significantly enhance the chances of contracting the disease. Other secondary factors include exposure to radiation, zeolite, simian virus 40 (SV40) and tobacco. We discuss each of these risk factors in more detail below.

Asbestos

Exposure to asbestos is the leading risk factor associated with mesothelioma. Asbestos is an insulating material comprised of magnesium-silicate mineral fibers. It was favored by builders and contractors for many years for its low heat conductivity and resistance to melting and burning. Since researchers have identified more and more links between mesothelioma and exposure to asbestos, the material is now less widely used. Prior to this discovery, however, millions of Americans have experienced serious exposure to this harmful substance.

Over 700,000 schools and buildings in the United States today contain asbestos insulation as reported by the US Environmental Protection Agency. Asbestos exposure doesn’t stop there, however. Asbestos is often found in ship yards, manufacturing facilities, railway facilities and construction sites. Blue collar workers are at the highest risk for developing mesothelioma due to occupational exposure and include those who work in mines, factories, shipyards, construction sites, railroads and for insulation manufacturers and gas mask manufacturers. The occupations most widely affected are miners, factory workers, railroad workers, ship builders and construction workers - especially those who install asbestos containing insulation. Sometimes family members related to the workers receive second hand exposure to asbestos from the dust and fibers that were brought home on the workers clothes and also become at risk for contracting mesothelioma.

Serpentine fibers and amphiboles are the 2 primary types of asbestos used. Chrysotile is a form of serpentine fiber and the most frequently used. These fibers tend to be curly and flexible. Amphibole fibers, however, are generally straight and thin and usually comprise one of five types: crocidolite, amosite, anthrophylite, tremolite, and actinolyte. The crocidolite type of Amphiboles is thought to be the leading contributor to cancer caused by asbestos. Serpentine fibers are dangerous as well, however, and have also been linked to mesothelioma.

Some research points to the fact that inhaled asbestos fibers cause a physical irritation resulting in cancer rather than the cancer being caused by a reaction that is more chemical in nature. As fibers are inhaled through the mouth and nose they are cleared from the body by adhering to mucus in the nose, throat and airways and then get expelled by coughing or swallowing. The Amphibole fibers (long and thin) do not clear as easily and it is therefore thought that they can embed into the lining of the lungs and chest and result in mesothelioma.

Asbestosis (scar tissue in the lungs) or lung cancer can also be caused by the inhalation of asbestos fibers. In fact, people exposed to asbestos are seven times more likely to develop lung cancer over the general public. Workers who sustain high levels of asbestos exposure are more likely to die from asbestosis, lung cancer or mesothelioma than any other disease. It is also believed that the action of coughing up and swallowing asbestos could contribute to a form of mesothelioma originating in the abdomen called peritoneal mesothelioma. Mesothelioma has been found to exist in other organs of the body as well such as the larynx, pancreas and colon, but those instances are extremely limited compared to lung cancer incidents.

The chance of developing mesothelioma is in direct proportion to the duration and amount of asbestos exposure that an individual sustains. Those who are exposed to high levels of asbestos at a young age, for long periods of time have a greater risk of being diagnosed with mesothelioma than those who have short, low level exposure. Another important consideration is that Mesothelioma can take a long time to manifest. Often, twenty to forty years can elapse from the time of exposure to diagnosis. Genetic factors can also play a role which explains why not everyone exposed to asbestos develops and asbestos related disease.

Radiation

Thorium dioxide (Thorotrast), a substance used in x-ray tests in the past has reported links to pleural mesothelioma and peritoneal mesothelioma. The use of Thorotrast has been discontinued for many years due to this discovery.

Zeolite

Some mesothelioma cases in the Anatoli region within Turkey have been linked to Zeolite, a silica based mineral with chemical properties similar to asbestos found in the soil there.

Simian Virus 40 (SV40)

Some scientists have found the simian virus 40 (SV30) in mesothelioma cells from humans and have been able to create mesothelioma in animals with the virus. The relationship between this virus and mesothelioma is still unclear, however, and further research is being conducted to gain clarity on this potential link.

Tobacco

Smoking alone is not linked to mesothelioma, but smokers who are exposed to asbestos have a much higher chance of developing lung cancer (as much as fifty to ninety percent higher). Research indicates that lung cancer is the leading cause of death among asbestos workers.

Mesothelioma Information

As with any disease or health condition, mesothelioma researchers have, over time, collected statistical information about mesothelioma. These statistics can help us learn about the proclivities of the disease and its incidence and potentially help future patients as we learn more about mesothelioma.

Incidence of Diagnosis

New cases of mesothelioma are diagnosed in between 2,500 and 3,000 Americans each year. These numbers, while significant, would indicate that mesothelioma is still a relatively rare disease, though incidence is expected to rise in the next decade according to projections.

Age at Diagnosis

The first diagnosis of mesothelioma typically occurs in men and women between the ages of 50 and 70 years. Mesothelioma patients, certainly, have been diagnosed at ages younger than 50 and older than 70, but diagnoses for those age groups are considered statistical anomalies.

Does Mesothelioma Occur in a Particular Sex or Racial Demographic More than Another?

Mesothelioma is much more common in men than women, due mostly to occupational asbestos exposure being more common among men of industrial labor sites. That is not to say, however, that women cannot be diagnosed with mesothelioma. In fact, recent evidence suggests that mesothelioma incidence in women may rise in the coming years as secondary exposures to asbestos can manifest in the form of a positive mesothelioma diagnosis. Also of note is that mesothelioma is much less common among African Americans than white Americans, the reasons for which researchers are still investigating.

What are Typical Patient Survival Rates Following a Mesothelioma Diagnosis?

As mesothelioma is often diagnosed in its advanced stages, the prognosis is sometimes poor with life expectancy being little more than a year following diagnosis. If diagnosed early enough however, patient prognoses increase dramatically. Patient survival rates are often contingent on the treatments available to the particular patient. Early-stage tumors eligible for surgical resection, for instance, will result in improved prognoses over those diagnosed with later-stage disease. As new therapies and treatments are researched and employed in the future, it is realistic to anticipate an improvement in patient survival rates.

Diagnosis

How do medical professionals diagnose mesothelioma?

If you believe that you may have mesothelioma, a qualified medical professional will use a variety of diagnostic tests and methods to confirm the presence of the disease.

Medical history review and exam

The first step that your health professional will take in evaluating you for an asbestos related disease is to obtain a full medical history to determine the level and severity of risk factors and presenting symptoms. This interview will look consider among other things, where you were exposed to asbestos, the length of exposure and the amount of asbestos that you were exposed to.

In addition, he/she will perform a medical exam to look for signs and symptoms of various forms of mesothelioma. For example, if pleural mesothelioma is suspected the doctor will look for fluid in the chest, peritoneal mesothelioma often shows fluid in the abdomen and pericardial mesothelioma presents with fluid in the area of the heart.

Diagnostic imaging tests

Chest x-rays are used to identify abnormalities in the lungs including unusual thickening, mineral deposits and fluid in the chest area. If these conditions are present then it may be evidence that mesothelioma has developed.

Diagnostic image tests like x-rays, CT scans and MRI's are useful in determining more information about the cancer including how far it is progressed. Each method provides another piece of information to your doctor to assist in making an accurate diagnosis. CT scans are capable of providing images of the same location from many different angles. MRI technology uses magnetic fields rather than x-ray to provide additional views.

Testing fluid and tissue samples

If fluid build-up in the chest, abdomen or heart area is present, your doctor may want to obtain a sample. To accomplish this he/she will use a long needle to obtain fluid from the target area. The fluid will then be sent to the lab for analysis.

If fluid build-up in the chest, abdomen or heart area is present, your doctor may want to obtain a sample. To accomplish this he/she will use a long needle to obtain fluid from the target area. The fluid will then be sent to the lab for analysis.

A bronchoscopy procedure may be recommended for patients who are suspected of having pleural mesothelioma. For this medical test, a soft tube illuminates the trachea and bronchi to determine if any masses are present in the airways. If deemed necessary, the technician my take sample of tissue that appears to be abnormal for further testing.

If lymph node involvement is suspected which is common with lung cancer, patients may also undergo a mediastinoscopy. This procedure is similar to a bronchoscopy in that a soft tube enters the body under the chest bone and illuminates the chest area. In this way, the surgeon can examine lymph nodes for abnormalities, check to see how far disease may have progressed and when necessary help diagnose lung cancer vs. mesothelioma.

Diagnosing mesothelioma is never easy. Fluid build up alone in the chest, belly or heart regions is not enough to confirm a diagnosis. Tissue samples obtained from biopsy procedures are also difficult to discern because mesothelioma cancer cells often resemble other types of cancer. For this reason, specialized laboratory procedures are often employed to identify certain chemicals that are known to exist with mesothelioma and high powered laboratory equipment is used to examine the smallest details of cancer cells to confirm that mesothelioma is present.