If you or your doctor suspects you or someone close to you might have mesothelioma, you're probably quite anxious. Only 2,000 to 3,000 new diagnoses of malignant mesothelioma cancer occur every year in the U.S., making it an uncommon but no longer rare form of cancer. Usually attributable to asbestos exposure sometime in the distant past, this type of cancer can take decades to mature into full-fledged cancer, and this period is called the "latency period" or "period of latency." Once it does, it is in most cases advanced, and the prognosis can be depressing. The procedure for getting a diagnosis of mesothelioma depends on your individual circumstances. Your doctor will probably conduct a medical history and do an exam to look for signs of mesothelioma, such as pleural effusion, ascites or pericardial efflusion. General screening is not usually done for mesothelioma, since it is so uncommon. Diagnostic tests are usually offered to those who are at risk or who develop symptoms.

Typically, the doctor will suspect mesothelioma when a patient comes in with symptoms and/or risk factors and only after other (more common) causes have been ruled out. If a doctor knows a patient has been exposed to asbestos in a work environment the doctor may test for mesothelioma earlier than if there was no known asbestos exposure or other major risk factors.

Image Scans

Some non-invasive tests that may be done initially, but that can't provide ultimate confirmation of a mesothelioma diagnosis, are:

• Chest x-ray: A chest x-ray is taken to look for abnormalities that may be signs of mesothelioma such as the thickening of the pleura, calcium deposits on the pleura, or pleural efflusion.
• CT scan of chest or abdomen (computed tomography): This scan is used to get an image of the affected area for possible clues to whether or not cancer is present. After mesothelioma has been diagnosed, CT scans help doctors figure out what stage it's in.)
• MRI scan (magnetic resonance imaging): Using radio waves and magnets, an MRI can help locate a tumor and reveal its dimensions.
• PET scan (positron emission tomography): This scan using very low doses of radioactive particles can help confirm or deny the results of a prior image test. Once a diagnosis of mesothelioma occurs, a PET scan can reveal whether it's metastasized, and if so, where.

Although they can detect damage caused by asbestos, and are helpful in monitoring treatment, there is debate as to how useful these scanning tests actually are for diagnostic purposes.

Blood Tests

Patients suspected of having mesothelioma also may receive blood tests. High levels of osteopontin and certain soluble peptides tend to be found in patients who have mesothelioma, but as yet blood tests for these substances are not used to diagnose mesothelioma, but rather as part of treatment.

Fluid Analysis and Biopsy

Another possible test is fluid analysis. A long needle is inserted into numbed skin over the chest, abdomen or heart, in procedures respectively called thoracentesis, paracentesis and pericardiocentesis. Pleural, thoracic or abdominal fluid is removed and analyzed. This test will not rule out cancer, but if cancer is present, it can help distinguish the presence of mesothelioma versus other types of cancer.

The next step may be a mesothelioma biopsy, the test that determines whether or not cancer is detected and is performed by a surgeon or oncologist. With a biopsy, the doctor takes fluid or tissue to test for malignant mesothelioma cells and has it analyzed for any abnormalities. The different possible biopsy procedures involve different ways to obtain a sample. The biopsy procedure used usually depends on where you are experiencing symptoms:

• Fine-needle aspiration: This procedure is done on an outpatient basis. A needle is inserted into the abdomen or the chest, guided by CT scans. There may not be a large enough sample to detect the mesothelioma using this method.
• Thoracoscopy: This procedure, done under general anesthesia, involves an incision or incisions in your chest and a tube with a video camera attached.
• Laparascopy: This is similar to thoracoscopy, but for the abdomen.
• Laparotomy: This surgical biopsy is full surgery to allow access to the abdomen for a tissue sample.
• Thoracotomy: This is full surgery as above, but for the chest.
• Bronchoscopy: Done with the patient under sedation, this procedure involves putting a tube down the throat to take a sample to test for possible pleural mesothelioma.

Once obtained, the biopsy sample is sent to a lab where a pathologist will look at it under a microscope. Lab tests to isolate mesothelioma and identify it apart from other types of cancer include immunohistochemistry tests, DNA microarray analysis, and electron microscopy.

Once a patient receives a diagnosis of mesothelioma, the pathologist will figure out what cellular type of mesothelioma it is. The next step is probably for the doctor to stage the cancer--that is, figure out how it's progressed, and determine treatment options. Whether the patient has malignant pleural mesothelioma, malignant peritoneal mesothelioma, or one of the less common types, the treatment stage can be an ardous and difficult time.