the thin layer of tissue that covers organs in the chest or abdomen.Malignant mesothelioma may be found in one or more of the following: the pleura, a thin layer of tissue that lines the chest cavity and covers the lungs the peritoneum, a thin layer of tissue that lines the abdomen and covers most of the organs in the abdomen the pericardium, a thin layer of tissue that surrounds the heart Malignant mesothelioma may also form in the heart or testicles, but this is rare.Malignant mesothelioma forms in the tissue that lines the chest or abdomen, including the pleura (the tissue that lines the chest cavity and covers the lungs) and the peritoneum (the tissue that lines the abdomen and covers most of the organs in the abdomen). Malignant mesothelioma may also form in the pericardium (the tissue that surrounds the heart) or the testicles, but this is rare.Being exposed to asbestos can increase the risk of malignant mesothelioma. Malignant mesothelioma is caused by certain changes to the way the cells that line the organs function, especially how they grow and divide into new cells. Often, the exact cause of the cell change is unknown. Learn more about how cancer develops at A risk factor is anything that increases the chance of getting a disease. Most people with malignant mesothelioma have worked or lived in places where they inhaled or swallowed asbestos, which has been used in the building and textile industries. After being exposed to asbestos, it usually takes a long time for malignant mesothelioma to form. Living with a person who works near asbestos is also a risk factor for malignant mesothelioma. Not every person with one or more of these risk factors will develop malignant mesothelioma. And it can develop in some people who don't have any known risk factors.Talk to your doctor if you think you may be at risk.Signs and symptoms of malignant mesothelioma include shortness of breath and pain under the rib cage. Sometimes the cancer causes fluid to collect in the chest or in the abdomen. Signs and symptoms may be caused by the fluid, malignant mesothelioma, or other conditions. Check with your doctor if you have any of the following:trouble breathingcoughpain under the rib cagepain or swelling in the abdomenlumps in the abdomenconstipation problems with blood clots (clots form when they shouldn't)weight loss for no known reasonfatigue (feeling very tired)Tests that examine the inside of the chest and abdomen are used to diagnose malignant mesothelioma.Sometimes it is hard to tell the difference between malignant mesothelioma in the chest and lung cancer. If you have symptoms that suggest mesothelioma, the doctor will need to find out if these are due to cancer or to another problem. The doctor will ask when the symptoms started and how often you have been having them. They will also ask about your personal and family health history and do a physical exam. Depending on these results, they may recommend other tests. If you are diagnosed with mesothelioma, the results of these tests will help you and your doctor plan treatment. The tests and procedures used to diagnose mesothelioma may include: Chest x-ray is a type of radiation that can go through the body and make pictures of the organs and bones inside the chest.A chest x-ray is used to take pictures of the structures and organs inside the chest. X-rays pass through the patient's body onto film or a computer.CT scan (CAT scan) uses a computer linked to an x-ray machine to make a series of detailed pictures of areas inside the body. The pictures are taken from different angles and are used to create 3-D views of tissues and organs. A dye may be injected into a vein or swallowed to help the organs or tissues show up more clearly. This procedure is also called computed tomography, computerized tomography, or computerized axial tomography. Learn more about . Biopsy is the removal of cells or tissues from the pleura or peritoneum so that a pathologist can view it under a microscope to check for signs of cancer. Procedures used to collect the cells or tissues include:Fine-needle (FNA) aspiration biopsy of the lung uses a thin needle to remove tissue or fluid. An imaging procedure is used to locate the abnormal tissue or fluid in the lung. A small incision may be made in the skin where the biopsy needle is inserted into the abnormal tissue or fluid, and a sample is removed.Fine-needle aspiration biopsy of the lung. The patient lies on a table that slides through the computed tomography (CT) machine, which takes x-ray pictures of the inside of the body. The x-ray pictures help the doctor see where the abnormal tissue is in the lung. A biopsy needle is inserted through the chest wall and into the area of abnormal lung tissue. A small piece of tissue is removed through the needle and checked under the microscope for signs of cancer. Thoracoscopy is surgery to look at the organs inside the chest to check for abnormal areas. An incision (cut) is made between two ribs, and a thoracoscope (a thin, tube-like instrument with a light and a lens for viewing) is inserted into the chest.Thoracotomy is surgery to look inside the chest. An incision (cut) is made between two ribs to check inside the chest for signs of disease.Peritoneoscopy is surgery to look inside the abdomen. An incision (cut) is made in the abdominal wall, and a peritoneoscope (a thin, tube-like instrument with a light and a lens for viewing) is inserted into the abdomen to check for signs of disease.Open biopsy is surgery to remove abnormal tissues so a pathologist can check it under a microscope for signs of disease. An incision (cut) is made through the skin to expose and remove the tissues. The following tests may be done on the cells and tissue samples that are taken:A cytologic exam is a laboratory test to view cells under a microscope to check for anything abnormal. For mesothelioma, fluid is taken from the chest or the abdomen. A pathologist checks the fluid for signs of cancer.Immunohistochemistry is a laboratory test that uses antibodies to check for certain antigens (markers) in a sample of a patient's tissue. The antibodies are usually linked to an enzyme or a fluorescent dye. After the antibodies bind to a specific antigen in the tissue sample, the enzyme or dye is activated, and the antigen can then be seen under a microscope. This type of test is used to help diagnose cancer and to help tell one type of cancer from another type of cancer.Electron microscopy is a laboratory test in which cells in a sample of tissue are viewed under a high-powered microscope to look for certain changes in the cells. An electron microscope shows tiny details better than other types of microscopes.After malignant mesothelioma has been diagnosed, tests are done to find out if cancer cells have spread to other parts of the body. The process used to find out if cancer has spread outside the pleura or peritoneum is called staging. The information gathered from the, Treatment for malignant mesothelioma may include surgery, radiation therapy, and chemotherapy, as well as targeted therapy and immunotherapy. The type of treatment you receive depends on many factors, including where the cancer is found and at what stage., Mesothelioma diagnosis may start with a physical exam. A healthcare professional may check for lumps or other signs. You might have imaging tests to look for mesothelioma. These could include a chest X-ray and a CT scan of your chest or belly..