Staging
Staging is the process of assessing how severe malignant mesothelioma is. It has been used to estimate a victim's prognosis (outlook), and to determine the most suitable therapy -- especially whether he is a suitable candidate for aggressive surgical procedures.

Staging is based on a number of characteristics of the disease, many of which need to be determined by invasive diagnostic procedures. There have been various staging systems proposed for malignant mesothelioma. Those in use now consider three main aspects of the disease (the TNM system):

T: primary tumor and the extent of its spread (no spread/local spread only/more distant but direct spread)
N: involvement of lymph nodes (nil/spread to nodes on the same side of the chest/spread to more nodes in the other side of the chest or more distantly)
M: whether there are metastases (distant spread of tumor via blood or lymph, not by direct extension).
Staging is commonly expressed from I (early disease, localized disease) to IV (widespread tumor, with involvement of lymph nodes and metastases