Those having symptoms will undergo a physical to determine whether there are additional signs of mesothelioma or asbestos lung cancer. Patients with pleural mesothelioma will often have pleural effusion (fluid in lungs). Some may have ascites (fluid in abdomine) in cases of peritoneal mesothelioma, or pericardial effusion (fluid in pericardium) in cases of pericardial mesothelioma. If the foregoing shows the potential for a diagnosis of mesothelioma, then other tests will be done, including imaging tests like x-rays, CT scans, MRI scans, and PET scans. Tests may reveal irregular thickening of pleura, calcium deposits or fluid in pleural space.  Tests may also allow the doctor to begin determining the extent of cancer (staging). If a pleural effusion, ascites or pericardial effusion is found, the doctor may sample fluid for diagnosing cancer by a pathologist. Also, tissue samples may be taken via thoracoscopy, laparoscopy, mediastinoscopy or bronchoscopy, or sometimes surgery, thoracotomy or laparotomy, may be done by a surgeon.

Mesothelioma is generally very difficult to diagnose and in all cases, I always recommend a biopsy. In case of death, I also recommend an autopsy. A great place for information on the symptoms and diagnosis of mesothelioma is the U.S. National Library of Medicine and the National Institutes for Health MedlinePlus: Mesothelioma page, which I used along with the American Cancer Society website in writing this.