CT demonstration of the 1996 AJCC-UICC regional lymph node classification for lung cancer staging

The new international lymph node classification adopted by the American Joint Committee on Cancer (AJCC) and the Union Internationale Contre le Cancer (UICC) is described and illustrated with computed tomography (CT). Anatomic landmarks for 14 hilar, intrapulmonary, and mediastinal lymph node stations are designated. Main differences between the new international classification and the American Thoracic Society (ATS) one are emphasized. In particular, mediastinal pleural reflection is now used to differentiate N2 from N1 nodes. The ATS 10L (left peribronchial nodes) and 10R (right tracheobronchial nodes) stations are now replaced by the AJCC-UICC station 10 (hilar nodes) and the AJCC-UICC station 4 (lower paratracheal, including azygos, nodes), respectively. This very important difference from the ATS classification helps classify the 4 lower paratracheal nodes as N2 nodes, even though the pleural reflection is not seen with CT. The 5 AJCC-UICC nodes are renamed subaortic nodes instead of aortopulmonary ATS nodes. Paraortic nodes, which previously were classified as 5 ATS nodes, are now included with the 6 AJCC-UICC nodes (now renamed paraaortic nodes instead of anterior mediastinal ATS nodes). This change helps accurate labeling because the border between 5 and 6 ATS nodes was not always clear on CT scans. Radiologists should be familiar with this new classification to be able to more accurately compare the lung cancer staging done in different institutions around the world.