Staging allows the patient and doctor to determine treatment options. Staging is divided into 3 areas, designated by the capital letters TNM:

• T refers to whether the original tumor has exceeded its margins.

• N stands for lymph nodes that are affected.

• M refers to metastasis to other areas of the body.

Pleural mesothelioma is further divided into overall stages:

Stage I -The cancer is present only on the pleura of the chest wall and the outer lining of the lungs.

Stage II-The cancer has spread into the lining of the lung, the internal lung tissues, or the diaphragm.

Stage III-The cancer has invaded chest lymph nodes, or has not yet invaded lymph nodes but has spread to the mediastinum or the outer layer of the heart.

Stage IV-The cancer is present in adjacent structures, with or without spread to remote areas of the body.