You might have a number of tests to investigate your symptoms and confirm a diagnosis of mesothelioma, including: 

• medical history and physical examination – a physical exam can pick up a pleural effusion, which is often the earliest sign of asbestos-related disease 
• biopsy, where a small sample of tissue is taken from the pleura surrounding the lungs for examination under a microscope  
• chest X-ray – this can pick up an abnormal thickening of the pleura or a pleural effusion 
• computed tomography (CT) scan of the chest, which uses a series of X-rays to make a detailed picture of the chest – this can show the exact location of the cancer, its size and how far it has spread 
• thoracentesis, a type of biopsy that removes a sample of fluid from the pleural cavity (the space between the two layers of pleura surrounding the lungs) for testing – this is done under local anaesthetic 
• blood tests – You will have blood tests to check your general health and help with making decisions about your treatment. Mesothelioma usually doesn’t show up on a blood test, but your doctor may look for substances (called tumour markers) that are produced by cancer cells. 

A biopsy of the pleural tissue is often done using a small cut in the chest into which a thorascope is inserted. A thorascope is a thin, tube-like instrument that has a light and a camera for viewing, as well as a tool to remove the tissue sample. This procedure – called thoracoscopic biopsy – is done under general anaesthetic in an operating theatre. 
 
If mesothelioma is diagnosed, pulmonary function tests might be used to see how well your lungs are working. This can be important if surgery to remove part of a lung might be used to treat the cancer. Pulmonary function tests involve breathing in and out through a tube connected to a machine. 

Stages of mesothelioma 

If you are diagnosed with mesothelioma, you might have more tests to determine the stage of the disease and whether the cancer has spread to other parts of the body. Knowing the stage of the disease helps your medical team plan the best treatment for you. 
 
Mesothelioma is divided into four stages: 

• Stage I – cancer has not spread from the pleura where it started 
• Stage II – cancer has spread into the lung tissue and/or the diaphragm (the muscle at the bottom of the chest cavity that is used for breathing) and has involved the lymph nodes on the same side of the lung, but not to distant sites 
• Stage III – cancer has spread further, including possibly to deeper lymph nodes between the lungs or in the neck, but has not spread to distant sites 
• Stage IV – cancer has spread to distant organs 

Tests to determine the stage of mesothelioma can include: 

• chest and abdominal CT scan 
• chest magnetic resonance imaging (MRI), which uses a magnet and radio waves to make images of parts of the body 
• positron emission tomography (PET) scan, which takes pictures of areas of the body after a radioactive sugar has been injected into the blood – cancer cells take up the sugar more intensely than other cells and can be seen in the images 
• thoracoscopic biopsy 
• laparoscopy, where a laparoscope (a thin, lighted tube with a lens for viewing and tools to remove samples of tissue) is inserted through a small cut in the abdomen