Mesothelioma: Questions and Answers 

Mesothelioma is a rare form of cancer in which malignant (cancerous) cells are found in the 

mesothelium, a protective sac that covers most of the body’s internal organs. Most people who 

develop mesothelioma have worked on jobs where they inhaled asbestos particles. 

1. What is the mesothelium?

The mesothelium is a membrane that covers and protects most of the internal organs of 

the body. It is composed of two layers of cells: One layer immediately surrounds the 

organ; the other forms a sac around it. The mesothelium produces a lubricating fluid that 

is released between these layers, allowing moving organs (such as the beating heart and 

the expanding and contracting lungs) to glide easily against adjacent structures. 

The mesothelium has different names, depending on its location in the body. The 

peritoneum is the mesothelial tissue that covers most of the organs in the abdominal 

cavity. The pleura is the membrane that surrounds the lungs and lines the wall of the 

chest cavity. The pericardium covers and protects the heart. The mesothelial tissue 

surrounding the male internal reproductive organs is called the tunica vaginalis testis. 

The tunica serosa uteri covers the internal reproductive organs in women. 

2. What is mesothelioma?

 

Mesothelioma (cancer of the mesothelium) is a disease in which cells of the mesothelium 

become abnormal and divide without control or order. They can invade and damage 

nearby tissues and organs. Cancer cells can also metastasize (spread) from their original 

site to other parts of the body. Most cases of mesothelioma begin in the pleura or 

peritoneum. 

3. How common is mesothelioma?

 

Although reported incidence rates have increased in the past 20 years, mesothelioma is 

still a relatively rare cancer. About 2,000 new cases of mesothelioma are diagnosed in 

the United States each year. Mesothelioma occurs more often in men than in women and 

risk increases with age, but this disease can appear in either men or women at any age. 

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4. What are the risk factors for mesothelioma?

Working with asbestos is the major risk factor for mesothelioma. A history of asbestos 

exposure at work is reported in about 70 percent to 80 percent of all cases. However, 

mesothelioma has been reported in some individuals without any known exposure to 

asbestos. 

Asbestos is the name of a group of minerals that occur naturally as masses of strong, 

flexible fibers that can be separated into thin threads and woven. Asbestos has been 

widely used in many industrial products, including cement, brake linings, roof shingles, 

flooring products, textiles, and insulation. If tiny asbestos particles float in the air, 

especially during the manufacturing process, they may be inhaled or swallowed, and can 

cause serious health problems. In addition to mesothelioma, exposure to asbestos 

increases the risk of lung cancer, asbestosis (a noncancerous, chronic lung ailment), and 

other cancers, such as those of the larynx and kidney. 

Smoking does not appear to increase the risk of mesothelioma. However, the 

combination of smoking and asbestos exposure significantly increases a person’s risk of 

developing cancer of the air passageways in the lung. 

5. Who is at increased risk for developing mesothelioma?

Asbestos has been mined and used commercially since the late 1800s. Its use greatly 

increased during World War II. Since the early 1940s, millions of American workers 

have been exposed to asbestos dust. Initially, the risks associated with asbestos exposure 

were not known. However, an increased risk of developing mesothelioma was later 

found among shipyard workers, people who work in asbestos mines and mills, producers 

of asbestos products, workers in the heating and construction industries, and other 

tradespeople. Today, the U.S. Occupational Safety and Health Administration (OSHA) 

sets limits for acceptable levels of asbestos exposure in the workplace. People who work 

with asbestos wear personal protective equipment to lower their risk of exposure. 

The risk of asbestos-related disease increases with heavier exposure to asbestos and 

longer exposure time. However, some individuals with only brief exposures have 

developed mesothelioma. On the other hand, not all workers who are heavily exposed 

develop asbestos-related diseases. 

There is some evidence that family members and others living with asbestos workers 

have an increased risk of developing mesothelioma, and possibly other asbestos-related 

diseases. This risk may be the result of exposure to asbestos dust brought home on the 

clothing and hair of asbestos workers. To reduce the chance of exposing family members 

to asbestos fibers, asbestos workers are usually required to shower and change their 

clothing before leaving the workplace. 

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6. What are the symptoms of mesothelioma?

 

Symptoms of mesothelioma may not appear until 30 to 50 years after exposure to 

asbestos. Shortness of breath and pain in the chest due to an accumulation of fluid in the 

pleura are often symptoms of pleural mesothelioma. Symptoms of peritoneal 

mesothelioma include weight loss and abdominal pain and swelling due to a buildup of 

fluid in the abdomen. Other symptoms of peritoneal mesothelioma may include bowel 

obstruction, blood clotting abnormalities, anemia, and fever. If the cancer has spread 

beyond the mesothelium to other parts of the body, symptoms may include pain, trouble 

swallowing, or swelling of the neck or face. 

These symptoms may be caused by mesothelioma or by other, less serious conditions. It 

is important to see a doctor about any of these symptoms. Only a doctor can make a 

diagnosis. 

7. How is mesothelioma diagnosed?

Diagnosing mesothelioma is often difficult, because the symptoms are similar to those of 

a number of other conditions. Diagnosis begins with a review of the patient’s medical 

history, including any history of asbestos exposure. A complete physical examination 

may be performed, including x-rays of the chest or abdomen and lung function tests. A 

CT (or CAT) scan or an MRI may also be useful. A CT scan is a series of detailed 

pictures of areas inside the body created by a computer linked to an x-ray machine. In an 

MRI, a powerful magnet linked to a computer is used to make detailed pictures of areas 

inside the body. These pictures are viewed on a monitor and can also be printed. 

A biopsy is needed to confirm a diagnosis of mesothelioma. In a biopsy, a surgeon or a 

medical oncologist (a doctor who specializes in diagnosing and treating cancer) removes 

a sample of tissue for examination under a microscope by a pathologist. A biopsy may 

be done in different ways, depending on where the abnormal area is located. If the cancer 

is in the chest, the doctor may perform a thoracoscopy. In this procedure, the doctor 

makes a small cut through the chest wall and puts a thin, lighted tube called a 

thoracoscope into the chest between two ribs. Thoracoscopy allows the doctor to look 

inside the chest and obtain tissue samples. If the cancer is in the abdomen, the doctor 

may perform a peritoneoscopy. To obtain tissue for examination, the doctor makes a 

small opening in the abdomen and inserts a special instrument called a peritoneoscope 

into the abdominal cavity. If these procedures do not yield enough tissue, more extensive 

diagnostic surgery may be necessary. 

If the diagnosis is mesothelioma, the doctor will want to learn the stage (or extent) of the 

disease. Staging involves more tests in a careful attempt to find out whether the cancer 

has spread and, if so, to which parts of the body. Knowing the stage of the disease helps 

the doctor plan treatment. 

Mesothelioma is described as localized if the cancer is found only on the membrane 

surface where it originated. It is classified as advanced if it has spread beyond the 

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original membrane surface to other parts of the body, such as the lymph nodes, lungs, 

chest wall, or abdominal organs. 

 

8. How is mesothelioma treated?

Treatment for mesothelioma depends on the location of the cancer, the stage of the 

disease, and the patient’s age and general health. Standard treatment options include 

surgery, radiation therapy, and chemotherapy. Sometimes, these treatments are 

combined. 

 

• Surgery is a common treatment for mesothelioma. The doctor may remove part of 

the lining of the chest or abdomen and some of the tissue around it. For cancer of the 

pleura (pleural mesothelioma), a lung may be removed in an operation called a 

pneumonectomy. Sometimes part of the diaphragm, the muscle below the lungs that 

helps with breathing, is also removed. 

• Radiation therapy, also called radiotherapy, involves the use of high-energy rays to 

kill cancer cells and shrink tumors. Radiation therapy affects the cancer cells only in 

the treated area. The radiation may come from a machine (external radiation) or from 

putting materials that produce radiation through thin plastic tubes into the area where 

the cancer cells are found (internal radiation therapy). 

• Chemotherapy is the use of anticancer drugs to kill cancer cells throughout the body. 

Most drugs used to treat mesothelioma are given by injection into a vein (intravenous, 

or IV). Doctors are also studying the effectiveness of putting chemotherapy directly 

into the chest or abdomen (intracavitary chemotherapy). 

To relieve symptoms and control pain, the doctor may use a needle or a thin tube to drain 

fluid that has built up in the chest or abdomen. The procedure for removing fluid from 

the chest is called thoracentesis. Removal of fluid from the abdomen is called 

paracentesis. Drugs may be given through a tube in the chest to prevent more fluid from 

accumulating. Radiation therapy and surgery may also be helpful in relieving symptoms. 

9. Are new treatments for mesothelioma being studied?

Yes. Because mesothelioma is very hard to control, the National Cancer Institute (NCI) 

is sponsoring clinical trials (research studies with people) that are designed to find new 

treatments and better ways to use current treatments. Before any new treatment can be 

recommended for general use, doctors conduct clinical trials to find out whether the 

treatment is safe for patients and effective against the disease. Participation in clinical 

trials is an important treatment option for many patients with mesothelioma. 

People interested in taking part in a clinical trial should talk with their doctor. 

Information about clinical trials is available from the Cancer Information Service (CIS) 

(see below) at 1–800–4–CANCER. Information specialists at the CIS use PDQ®, NCI’s 

cancer information database, to identify and provide detailed information about specific 

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ongoing clinical trials. Patients also have the option of searching for clinical trials on 

their own. The clinical trials page on the NCI’s Cancer.gov Web site, located at 

http://www.cancer.gov/clinicaltrials on the Internet, provides general information about 

clinical trials and links to PDQ. 

People considering clinical trials may be interested in the NCI booklet Taking Part in 

Cancer Treatment Research Studies. This booklet describes how research studies are 

carried out and explains their possible benefits and risks. The booklet is available by 

calling the CIS, or from the NCI Publications Locator Web site at 

http://www.cancer.gov/publications on the Internet. 

# # # 

Related NCI materials and Web pages: 

• National Cancer Institute Fact Sheet 3.21, Asbestos Exposure: Questions and 

Answers (http://www.cancer.gov/cancertopics/factsheet/Risk/asbestos)

• Clinical Trials Home Page (http://www.cancer.gov/clinicaltrials)

• Malignant Mesothelioma Home Page 

(http://www.cancer.gov/cancertopics/types/malignantmesothelioma)

• Taking Part in Cancer Treatment Research Studies

(http://www.cancer.gov/clinicaltrials/Taking-Part-in-Cancer-Treatment-ResearchStudies)

For more help, contact: 

NCI’s Cancer Information Service 

Telephone (toll-free): 1–800–4–CANCER (1–800–422–6237) 

TTY (toll-free): 1–800–332–8615

LiveHelp® online chat: https://cissecure.nci.nih.gov/livehelp/welcome.asp

This fact sheet was reviewed on 5/13/02 

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