There are a number of different staging systems for malignant mesothelioma, including a TNM system. All list four stages of tumor from very localized to metastatic, but no one system is universally agreed upon. The PDQ classification into localized and advanced disease seems most appropriate for decision-making.
There is no satisfactory staging system for peritoneal mesothelioma, although the tumor is usually confined to the abdomen. Since metastasis is rare, extensive staging studies outside the abdomen may not be necessary. CT scans will usually adequately define the extent of tumor.
