Diagnosing mesothelioma is frequently difficult, because the symptoms are indistinguishable to those of a figure of other conditions. Diagnosis starts with an audit of the patient's medical history. A history of exposure to asbestos may boost clinical suspicion for mesothelioma. A physical inspection is executed, chased via chest X-ray and frequently lung operate tests. The X-ray may disclose pleural thickening normally perceived afterwards asbestos exposure and boosts suspicion of mesothelioma. A CT (or CAT) scans or an MRI is generally performed. If a great quantity of liquid is current, abnormal cells may be detected via cytopathology whether this liquid is aspirated with a syringe. For pleural liquid, this is done via thoracentesis or tube thoracostomy for ascites, with paracentesis or ascitic drain; and for pericardial effusion with pericardiocentesis. While absence of malignant cells on cytology does not fully exclude mesothelioma, it produces it much more improbable, notably whether a choice diagnosis
can be prepared (e.g. tuberculosis, heart failure). Unfortunately, the diagnosis of malignant mesothelioma via cytology alone is difficult, even with master pathologists.

Generally, a biopsy is lacked to make sure a diagnosis of malignant mesothelioma. A nurse withdraws a poll of tissue for inspection beneath a microscope via a pathologist. A biopsy may be done in unlike ways, depending on where the abnormal field is located. If the cancer is in the chest, the nurse may conduct a thoracoscopy. In this method, the nurse produces a small cut through the chest wall and puts a lean, lighted tube paged a thoracoscope into the chest between pair ribs. Thoracoscopy permits the nurse to appearance indoor the chest and receive tissue samples. Alternatively, the chest surgeon might immediately frank the chest (thoracotomy). If the cancer is in the abdomen, the nurse may conduct a laparoscopy. To receive tissue for inspection, the nurse produces a small incision in the abdomen and introduces a special instrument into the abdominal cavity. If these methods do not output enough tissue, more extensive diagnostic medicine may be necessary.

Immunohisto chemical studies play an significant role for the pathologist in distinguishing malignant mesothelioma from neoplastic mimics. There are many checks and panels available. No single trial is ideal for distinguishing mesothelioma from carcinoma or even benign versus malignant.