MesotheliomaWhat is Mesothelioma?
Stages of Mesothelioma
In order for doctors to maintain consistency when determining what stage the cancer is in, different staging processes have been developed. Mesothelioma is staged using several different imaging studies such as x-rays, CT scans, and MRI scans. Typically, treatment and outlook for patients with mesothelioma depends on how extensively the size of the primary tumor, and how far the cancer has metastasized or spread throughout their bodies. Because pleural mesothelioma is the most common mesothelial cancer, it is type of mesothelioma for which a staging system has been developed.
The staging system most often used for mesothelioma is the Butchart system. This system is based mainly on the extent of the primary tumor mass, and divides mesotheliomas into stages I through IV.
Butchart Staging System
Stage I: Cancerous cells are present within the right or left pleural mesothelial tissue, and may also be present in the lung, pericardium or diaphragm on the same side.
Stage II: Mesothelioma invades the chest wall or involves the esophagus, heart, or pleura on both sides. The lymph nodes in the chest may also be involved.
Stage III: Mesothelioma has penetrated through the diaphragm into the peritoneum (abdominal cavity lining of the abdominal cavity). Lymph nodes beyond those in the chest may also be involved. Mesothelioma has penetrated through the diaphragm into the peritoneum (lining of the abdominal cavity). Lymph nodes beyond those in the chest may also be involved.
Stage IV: There is evidence of distant metastases (cancer cells spreading through the bloodstream to other organs).
TNM Staging System
The THM system, another system of mesothelioma staging, has recently been approved by the American Joint Committee on Cancer (AJCC). T represents tumor size and how far it has spread to nearby organs, N stands for lymph nodes and M represents metastasis. In TNM staging, information about the tumor, lymph nodes, and metastasis is combined in a process called stage grouping to assign a stage described by Roman numerals from I to IV. Minor differences exist between the AJCC TNM staging system and the Butchart staging system.
Stage I: Cancerous cells are present within the right or left pleural mesothelial tissue, and may also be present in the lung, pericardium or diaphragm on the same side. It has not yet spread to the lymph nodes.
Stage II: Cancerous cells have spread from the pleura on one side to the nearby peribronchial and/or hilar lymph nodes next to the lung on the same side. It may also have spread into the lung, pericardium, or diaphragm on the same side.
Stage III: Cancerous cells have spread into the chest wall muscle, ribs, heart, esophagus, or other organs in the chest on the same side as the main tumor mass, with or without spread to subcarinal (windpipe) and/or mediastinal (chest area) lymph nodes on the same side as the main tumor.
Stage IV: Cancerous cells have spread into the lymph nodes in the chest on the side opposite that of the primary tumor, or directly extends to the pleura or lung on the opposite side, or directly extends into the peritoneum, or directly extends into organs in the abdominal cavity or neck. Any mesothelioma with proof of distant metastases (spread to other organs through the bloodstream) or spread to organs beyond the chest or abdomen is included in this stage.
Although the TNM classification is the most detailed and exact, the original Butchart staging system is still used most often to describe the spread of pleural mesothelioma. Understanding these staging systems for mesothelioma is crucial for both estimating and understanding prognosis, and also for assessing therapeutic options.
Prognostic Factors:
Typically, younger age at diagnosis, performance status (functional status) and absence of weight loss are associated with a more favorable prognosis.
Mesotheliomas are usually of three different cell types (histological analysis) each associated with different prognisis: 1) epithelial cell type - has the most favorable prognosis; 2) fibrosarcomatous cell type - carries the worst prognosis and 3) mixed cell type - has an intermediate prognosis.
