An oncologist, a doctor who specializes in diagnosing and treating cancer, performs a diagnosis of mesothelioma. A proper diagnosis includes an overview of the patient’s medical history with an emphasis on any history of exposure to asbestos. A physical examination that includes a check for lumps, chest x-rays and abdominal x-rays as well as lung functioning tests. A CAT scan or magnetic resonance imaging (MRI) may be used to view images and areas inside the body. A biopsy is then used to confirm the existence of mesothelioma. A biopsy involves the removal of tissue samples for examination. The extracted sample is then sent to a pathologist who is responsible to examine the tissue under a microscope.