Stage I mesothelioma is used to describe disease progression characterized by the presence of mesothelioma within the right or left pleura, which is the membrane that covers the lungs. The cancer may also be present, on the same side only, in the lung, pericardium, or diaphragm.
Stage 2 mesothelioma describes the state in which the cancer spreads to the extent of invading one or more additional areas, including the pleura on both sides, the chest wall, esophagus, heart, and/or lymph nodes in the chest.
Stage 3 mesothelioma indicates further spread of the cancer, involving penetration through the diagram into the peritoneum, which is the lining of the abdomen. This state my also involve additional lymph nodes beyond the chest area.
Stage 4 mesothelioma is the final state of mesothelioma, in which the cancer cells have gained entry to the bloodstream, enabling the disease to spread to other organs throughout the body. The process of spreading via the bloodstream is referred to as distant metastes.