Cancer starts when cells in the body change (mutate) and grow out of control. Your body is made up of tiny building blocks called cells. Normal cells grow when your body needs them and die when your body doesn't need them any longer.

Cancer is made up of abnormal cells that grow even though your body doesn't need them. In most cancers, the abnormal cells grow to form a lump or mass called a tumor. If cancer cells are in the body long enough, they can grow into (invade) nearby areas. They can also spread to other parts of the body (metastasize).

Malignant mesothelioma, often just called mesothelioma, is a rare kind of cancer. It starts in the mesothelium. This is a thin lining that covers organs and lines the inside of certain parts of the body. It most often starts in the lining of the chest and belly (abdomen).

The mesothelium is a lining that protects the outer surface of some organs. These include the lungs, stomach, and heart. It also lines the inside of your chest and abdomen.

The mesothelium makes fluid that helps the organs move against each other inside your body. For instance, it helps your lungs to slide inside your chest when you breathe.

The mesothelium has different names in different parts of the body:

• The lining in the chest cavity and covering the lungs is the  pleura.

• The lining in the abdomen is the  peritoneum.

• The lining around the heart is the  pericardium.

• The lining around the testicles is the  tunica vaginalis .

Mesothelioma can start in any of these linings. It’s most common in the chest. This is called pleural mesothelioma. The next most common place is the abdomen. There it’s called peritoneal mesothelioma.

Mesotheliomas can be grouped based on how the cancer cells look under a microscope:

• The  epithelioid type is the most common. It also tends to have a better outlook than the other types.

• The  sarcomatoid or fibrous type tends to be harder to treat. It's not common.

• The  mixed (biphasic) type has both epithelioid and sarcomatoid areas. It tends to have an outlook in between the other two types.

Mesothelioma starts in the thin lining around certain organs. Unlike many other kinds of cancer, it usually doesn’t grow as a single large tumor. Instead, it often grows along the lining at first. Over time, it can affect how well the lining works, which can lead to symptoms. For instance, if the cancer starts in the lining around the lungs, it can spread and affect their ability to expand. This can cause symptoms, such as shortness of breath or chest pain. As it grows, the cancer can spread into nearby organs or other parts of the body, such as lymph nodes, bones, or the liver.

If you have questions about mesothelioma, talk with your healthcare provider. Your provider can help you understand more about this cancer.

You may have questions and concerns about your treatment options. You may also want to know how you’ll feel, how your body will work after treatment, and if you’ll have to change your normal activities.

Your healthcare provider is the best person to answer your questions. They can explain what your treatment choices are, the goals of treatment, how well treatment is expected to work, and what the risks and side effects may be.

Your healthcare provider may advise a certain treatment. Or they may offer more than one and ask you to decide which one you’d like to use. It can be hard to make this decision. It’s important to take the time you need to make the best choice.

Deciding on the best plan may take some time. Talk with your healthcare provider about how much time you can take to explore your options. You may want to get a second opinion before deciding on your treatment plan. You may also want to include your partner, spouse, family, or friends in this process.

For some people with mesothelioma, the goal of treatment is to cure the cancer. If a cure isn’t possible, treatment can be used to shrink the cancer or help keep it under control. Treatment can also improve your quality of life by helping to control symptoms caused by the disease. The goals of treatment can include one or more of these things:

• Remove or destroy the mesothelioma in the place where it started while doing as little damage as possible to nearby areas

• Kill the cancer cells or keep them from growing or spreading

• Help prevent or delay the cancer's return

• Ease symptoms caused by the cancer, such as pain, trouble breathing, or swallowing problems

Treatment for cancer is either local or systemic. You may have both.

• Local treatments remove, destroy, or control cancer cells in a certain place in the body. Surgery and radiation are local treatments.
• Systemic treatments destroy or control cancer cells throughout the body. Chemotherapy and targeted therapy are examples.

Here’s a list of common mesothelioma treatments:

Researchers are always looking for new ways to treat mesothelioma. These new methods are tested in clinical trials. Taking part in a clinical trial means you get the best treatment available today, and you might also get new treatments that are thought to be even better. Before starting treatment, talk with your healthcare provider to find out if there are any clinical trials you should think about.

Most experts agree that treatment in a clinical trial should be considered for any type or stage of mesothelioma.

At first, thinking about treatment options may seem overwhelming. Talk with your healthcare team and loved ones. Make a list of questions. Consider the benefits and side effects of each option. Discuss your concerns with your healthcare provider before making a decision.