For years, medical researchers have studied cancer and monitored its progression in terms of stages, which allows doctors to determine the extent the patient's cancer and how far has it has spread. The proper staging of cancer is critical in allowing the oncologist to determine the best course of mesothelioma treatment.

Below is a general list of mesothelioma stages a patient may experience:

• Stage 1 - Mesothelioma affects the outer layer of the pleura around the chest wall, usually on one side of the chest only. It may have grown in the pleural tissue covering the diaphragm. It is possible for the mesothelioma cancer to start spreading to the inner pleural layer, which is closest to the lungs.

• Stage 2 - Mesothelioma has spread to both layers of the pleura on one side of the body or to the chest wall. The esophagus and diaphragm muscles may also be affected.

• Stage 3 - Mesothelioma has penetrated into the lining of the peritoneum or abdominal cavity, or has possibly spread to the lymph nodes in the chest.

• Stage 4 - At this point, it is very unlikely mesothelioma can be removed through surgery, as the cancer has spread to different areas of the body, in the bloodstream, or to different organs.