Understanding Mesothelioma

What is cancer?

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Under normal conditions, the cells in the human body divide and grow in an orderly, controlled manner. Cancer occurs when cells become abnormal and rapidly form more cells in an uncontrolled way, forming a mass of tissue. This mass of tissue is called a tumor, or lesion.

Tumors can either be malignant or benign. Malignant tumors can invade surrounding tissue. Cells from malignant tumors can also break away, usually by way of the bloodstream, and travel to other parts of the body, where new tumors may form. This is how cancer spreads. The term for this is metastasis. A tumor that forms in this way is always made up of cells like those of the original site.

When a tumor is not malignant, it is called a benign tumor. Benign tumors can often be removed with surgery and usually do not recur. The cells in benign tumors do not invade other tissues or spread to other parts of the body. In other words, these tumors do not typically metastasize.

What is mesothelioma?

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Mesothelioma is a rare form of cancer that arises in the mesothelium. The mesothelium is made up of visceral and parietal membranes (thin layers of tissue), which surround organs and body cavities, such as the lungs or abdomen. The visceral membrane immediately surrounds the organ, and the parietal membrane is a sac covering the visceral membrane. There is a lubricating fluid between these membranes that make up the mesothelium. This fluid helps organs move easily among surrounding structures. In the case of the lung, it helps reduce friction between the lung and chest wall during normal breathing as the lung expands. There are different types of mesothelioma, depending where it is found in the body. In the abdomen, it is called peritoneal mesothelioma; on the lungs, it is called pleural mesothelioma; and if it develops on the heart, pericardial mesothelioma.

What causes mesothelioma?

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Asbestos is a major known cause

Studies show that asbestos is a major cause of mesothelioma. By various estimates, it accounts for about 75–80% of all mesothelioma cases in the United States. Asbestos is a mineral that occurs as a long, thin fiber in the environment. Before its usage was banned due to health dangers in the 1980s, it was used in many industrial and insulation materials as a fire retardant. Some of the jobs in which people have been exposed to asbestos directly or indirectly are those that involve factory work, demolition, insulation, shipbuilding, carpentry, and installation of brake linings in vehicles. Despite rigorous efforts to eliminate asbestos from our environment, some public and private buildings still contain asbestos. Personnel who remove asbestos from such structures or work around asbestos are required to wear personal protective equipment to lower their risk of exposure.

Asbestos fibers may be inhaled and become lodged in the lungs, which can cause damage. If swallowed, asbestos may lead to peritoneal mesothelioma. Scientists are still researching exactly how asbestos fibers cause mesothelioma. It may be by a direct action on the cells of the body or by forming substances that affect genes in the body.
There may be other causes

Although asbestos is the major cause of mesothelioma, up to 30–50% of all cases are not obviously related to prior asbestos exposure. Other possible causes include prior exposure to radiation or to certain minerals closely related to asbestos that are found in the soil. Smoking has not been shown to be a cause of mesothelioma. However, if a smoker has also been exposed to asbestos, this greatly increases his or her risk of developing other types of lung cancer.

What are the facts about mesothelioma?

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It takes a long time to develop
Mesothelioma is characterized by having a long latency period, which means that symptoms don’t develop for 20–50 years after environmental exposure. The average age at which symptoms usually begin to appear is around 60 years old.

It is a relatively rare disease
An estimated 2,000 to 3,000 cases of mesothelioma are diagnosed each year in the US. In other countries, the number of cases differs. Overall, the number of cases reported each year appears to be increasing.

It occurs in men more than in women
Mesothelioma affects men about three times more often than women in the US. Incidence rises steadily with age. In other parts of the world, where exposure comes primarily from other environmental sources, such as in Turkey, mesothelioma occurs about equally in men and women.

It develops mostly on the lungs
The most common place for mesothelioma to develop is on the lungs. About two-thirds of all mesothelioma cases develop in the pleural mesothelium. This mesothelioma on the lungs is called malignant pleural mesothelioma (MPM). The remaining cases develop in the peritoneal mesothelium in the abdomen. A tumor in the abdominal mesothelium is called peritoneal mesothelioma. Rarely, mesothelioma occurs in other mesothelial tissue, such as on the heart or on the reproductive organs.

What are the symptoms of mesothelioma?

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The most common symptoms of pleural mesothelioma (mesothelioma on the lungs) are difficulty in breathing, chest pain, or both. Occasionally, a patient may not have symptoms at diagnosis. In addition to a general feeling of not being well, other less common symptoms include:

• weight loss
• fever
• night sweats
• cough

Symptoms of peritoneal mesothelioma (mesothelioma in the abdomen) may include:

• swelling
• pain due to accumulation of fluid in the abdominal cavity
• weight loss
• a mass in the abdomen
• bowel obstruction
• fever

How is mesothelioma diagnosed?

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Diagnosing mesothelioma can be difficult because many of the symptoms are similar to those of a number of other conditions, including other types of cancer. At the time of diagnosis, your doctor will first do a physical examination and complete a medical history.

Diagnosis and testing

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Several tests can be used to help in making the diagnosis of mesothelioma, including a chest x-ray, a CT scan, and a MRI scan. A chest x-ray yields an image of the lungs that will show many types of abnormal changes. A CT scan (computed tomography) is a type of x-ray, but it uses a computer rather than film and creates more detailed images than a x-ray. A MRI scan (magnetic resonance imaging) uses magnetism, radio waves, and a computer; and it does not use x-ray radiation. These tests help your doctor differentiate mesothelioma from other lung tumors as well as determine where the tumor is and its size.

Your doctor may need to remove a tissue sample from the tumor, which is called a biopsy, or draw fluid from the tumor to confirm the diagnosis. This can be done several ways.

The simplest way to obtain tissue samples is to make a small incision and place a flexible tube in the area of the tumor. When this procedure is done in the chest area it is called a thoracoscopy. When it is done in the abdominal cavity, it is called a laparoscopy. A tube with an attached small video camera is placed inside the body so the doctor can see the area in greater detail. A tissue sample may be taken at the same time. Sometimes, however, a more extensive surgical procedure may be advisable. A thoracotomy can be done through an incision in the chest to take a biopsy and, if feasible, to remove most or all of the visible tumor. If this procedure is done in the abdominal cavity, it is called a laparotomy.

At other times, a mediastinoscopy may be done in which a very small incision is made just above the sternum (breast bone) and a tube is inserted just behind the sternum. This lets the doctors look at lymph nodes. Lymph nodes are small, bean-shaped structures that are an important part of the body’s immune system, and they contain cells that help your body fight infection as well as cancer. This test will give the doctor more information on the type of cancer and whether it has spread to other areas. The tissue samples taken in these procedures are analyzed by looking at them under a microscope to determine whether the tumor is mesothelioma or another type of cancer.

What are the stages of mesothelioma?

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Mesothelioma tends to grow and spread in unusual ways compared to other tumors. Rather than forming a lump, mesothelioma tends to extend from the pleural lining to press against the lung or abdominal organs. It also grows along the pleural lining, eventually forming a hard casing around the lung (like the peel of an orange). This makes taking a deep breath difficult. Mesothelioma generally does not spread widely to other organs. It tends to involve the chest and lungs or abdominal cavity before spreading to other distant organs, late in the course of the disease. If the disease is detected early, when only limited growth on the pleural lining has occurred (stage I), the tumor is considered potentially curable, and an attempt can be made to surgically remove the entire tumor. Usually, however, the tumor is detected later, when it more extensively involves the pleural lining and has possibly invaded surrounding normal structures. In these advanced stages (stages II, III, and IV), the cancer may not be considered curable and is generally treated to extend survival and improve symptoms and quality of life.

What are treatment options for mesothelioma?

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The stage, size, and location of your tumor will determine how it is treated. Treatment options could include surgery, chemotherapy, immunotherapy, radiation therapy, or a combination of any of these, depending on the type and stage of cancer that you have.

For most types of tumors, surgical removal of the visible tumor is considered the treatment that gives the best chance of cure. The decision of whether to use surgery is dependent on the size and location of the tumor and on whether the cancer cells have spread to other parts of the body. If the tumor cells have spread or if some of the tumor could not be removed during surgery, one or more other therapies may then be used as the next best chance to improve survival.

Chemotherapy is treatment with medication most commonly given by injection into a vein to destroy or stop the growth of cancer cells. Many drugs have been used in the treatment of mesothelioma. Talk with your doctor about which chemotherapy would be best for your particular situation.

Radiation therapy is a treatment method that uses high-energy x-rays to destroy cancer cells and shrink tumors. It is also used to improve disease-related symptoms.

Immunotherapy is a treatment that stimulates or restores the ability of the immune system to fight infection and disease. It is also used to lessen side effects that may be caused by some cancer treatments. Other terms used to describe this or similar therapies are biotherapy (biological therapy) or biological response modifier (BRM) therapy.

There are many people researching other possible treatments for mesothelioma. Your health care team is your best source for gaining and understanding information regarding the treatment of your mesothelioma.

Glossary

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Benign - A term used to describe a tumor that is not malignant. Benign tumors can often be removed with surgery and usually do not recur.

Biopsy - The removal and examination of a sample of tissue from a living body for diagnostic purposes.

Chemotherapy - Anticancer drugs are used to destroy cancer cells and often are the only method capable of treating widespread disease. Chemotherapy may destroy cancer cells that have spread, or metastasized, to parts of the body far from where the tumor started.

Chest x-ray - Provides an image of the lungs or other parts of the chest that will show many types of abnormal changes.

CT Scan (computed tomography) - A type of x-ray that uses a computer rather than film and creates more detailed images than an x-ray does.

Immunotherapy (biotherapy) - Stimulates the body’s immune system to recognize, attack, and destroy cancer cells.

Laparoscopy - A way to examine a tumor through a small incision in the abdominal cavity using a tube attached to a small video camera. A tissue sample may be taken at the same time.

Laparotomy - An incision in the abdominal cavity to take a tissue sample and, if possible, to remove most or all of the visible tumor.

Lymph nodes - Small, bean-shaped structures that are an important part of the body’s immune system. Lymph nodes contain cells that help your body fight infection as well as cancer.

Malignant - Cancer that invades the tissue around it and/or spreads to other parts of the body.

Mediastinoscopy - A very small incision is made just above the sternum (breast bone), and a tube is inserted just behind the breast bone to examine the lymph nodes.

Mesothelioma - A rare form of cancer that arises in the mesothelium (thin layers of tissue that surround organs and body cavities, such as the lungs or abdomen). Mesothelioma is referred to by different names, depending on what part of the body it is found in:

peritoneal mesothelioma—mesothelioma in the abdomen
pleural mesothelioma—mesothelioma on the lungs
pericardial mesothelioma—mesothelioma on the heart

Mesothelium -Thin layers of tissue that surround organs and body cavities, such as the lungs or abdomen.

Metastasis - The spread of cancer from one part of the body to another.

MRI scan (magnetic resonance imaging) - Uses magnetism, radio waves and a computer to create an image of the lungs or other body parts. A MRI scan does not use x-ray radiation.

Radiation therapy - Uses x-rays to destroy cancer cells or damage them so much that they cannot multiply. Used alone or in combination with therapies such as surgery and chemotherapy.

Stage (staging) - The extent to which a cancer has spread from the original site to other parts of the body.

Surgical removal - An operation to remove the tumor.

Thoracoscopy - A way to examine a tumor through a small incision in the chest area using a tube attached to a video camera. A tissue sample may be taken at the same time.

Thoracotomy - An incision in the chest to take a tissue sample and, if possible, to remove most or all of the visible tumor.

Tumor - An abnormal growth of tissue. Tumors may be either benign (not cancerous) or malignant (cancerous)