Due to the fact that symptoms of mesothelioma are similar to those of a number of other conditions, it is often very difficult to diagnose the condition with certainty.

Upon visiting your doctor, the diagnostic process often begins with a review of the patient's medical history. A history of occupational exposure to asbestos (Asbestos has been widely used in many industrial products, including cement, brake linings, roof shingles, flooring products, textiles, and insulation) may increase clinical suspicion for mesothelioma.

After consideration of a patients actual exposure and probability of contamination, a physical examination is performed, followed by chest X-rays and more than likely, lung function tests. The X-rays may or may not reveal pleural thickening, which is commonly found after asbestos exposure and increases suspicion of mesothelioma. An MRI is usually also performed which is intended to identify whether fluid is present.

If any of the results are positive or further is regarded as suspicious, a biopsy is needed to confirm a diagnosis of mesothelioma. A biopsy is performed by a doctor who removes a sample of tissue for examination under a microscope. A biopsy may be done in different ways, depending on where the abnormal area is located. If the cancer is in the chest, the doctor may perform a thoracoscopy. In this procedure, the doctor makes a small cut through the chest wall and puts a thin, lighted tube called a thoracoscope into the chest between two ribs. Thoracoscopy allows the doctor to look inside the chest and obtain tissue samples.

If the cancer is in the abdomen, the doctor may perform a laparoscopy. To obtain tissue for examination, the doctor makes a small opening in the abdomen and inserts a special instrument into the abdominal cavity. If these procedures do not yield enough tissue, more extensive diagnostic surgery may be necessary.