An estimated 2,000-3,000 people are diagnosed with mesothelioma each year in the United States. The fact that mesothelioma may take 25-40 years after asbestos exposure to develop can make diagnosis tricky. Also making diagnosis difficult is the fact that many of the early mesothelioma symptoms are not specific to the disease and are very similar to symptoms of other diseases and conditions. People often think these are symptoms of some common, minor illness and do not seek medical attention right away. For that reason, most people are not diagnosed with mesothelioma for two to three months after they first notice symptoms.

There are many methods by which someone can be diagnosed with mesothelioma. A doctor may take a complete medical history to assess symptoms and risk factors, including determining whether the person has been exposed to asbestos. Some signs of mesothelioma may be found during a physical exam, but some require imaging studies. Therefore, the doctor may schedule chest x-rays, CT scans, and MRIs. These tests can also help determine the size, location, and extent of the cancer.

Doctors may also conduct blood tests to look for a certain protein called osteopontin that is elevated in people diagnosed with mesothelioma. If fluid has built up in the chest or abdomen, doctors may take a sample of the fluid and test it for cancer cells. If cancer cells are found, the doctors will need to conduct further tests to determine whether the cancer is mesothelioma, lung cancer, or another type of cancer.

Doctors may also conduct a biopsy in which they take samples of tissue from inside the chest or abdomen to check for cancer growth. Surgery may also allow doctors to take a larger sample of the tumor or the entire tumor. Doctors can also examine the lymph nodes to determine whether the cancer has spread to them. Since mesothelioma typically does not spread to the lymph nodes, finding cancer cells there can rule out mesothelioma.

After a person has been diagnosed with mesothelioma by one of these or other methods, doctors may conduct other tests to determine whether the cancer has spread. This process is called staging. Learn more about this on the Mesothelioma Stages page.