Summary: Any contralateral mediastinal nodal metastasis or any supraclavicular/scalene adenopathy remains classified as N3, regardless of the primary tumor location.
Station to Station: One of the most notable updates to the 9th edition of the TNM staging system for lung cancer is the formal subdivision of N2 disease: N2a *and* N2b. According to Dr. Girish Shroff’s update in our Cardiothoracic Imaging Case Review Online Course, the priority of now is the number of involved nodal stations, rather than absolute count of metastatic nodes:
- N0: No regional lymph node involvement.
- N1: Metastasis in ipsilateral bronchopulmonary or hilar nodes.
- N2: Metastasis in ipsilateral mediastinal and/or subcarinal nodes, now subdivided by station density:
- N2a—Involvement of a single N2 station.
- N2b—Involvement of multiple N2 stations.
- N3: Metastasis in contralateral mediastinal or contralateral hilar nodes, or any supraclavicular/scalene nodes.
Stations > Counts: Even if a patient presents with multiple metastatic nodes, they are staged as N2a if all involved nodes reside within a single station (e.g., lower right paratracheal region).
- Metastatic involvement of both station 5 and station 6 automatically elevates to N2b.
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