Lung cancer: update on staging classifications.

The AJC for Cancer Staging has improved the TNM system for lung cancer by breaking up the large category of advanced disease into several groups with different treatment implications. Radiologists should be familiar with this system so that they can direct the imaging part of the workup efficiently. The ATS classification of regional lymph nodes also has been updated both to take into account the growing recognition of superior diaphragmatic nodes in lung cancer and to change the supraclavicular lymph nodes from distant metastases to thoracic nodes (in keeping with the revised TNM system). Use of this classification helps radiologists record accurately which nodes are involved and also prompts the film reader to examine all parts of the mediastinum carefully and systematically. The use of CT for staging lung cancer is well established, but its appropriate use and limitations should be recognized. The usefulness of MR in special cases is now well described, but the hoped-for tissue specificity for tumor has not been realized. Imaging techniques have a primary role in screening for spread of disease, but confirmation by tissue biopsy is a required step in correct management.