Distribution of mediastinal lymph node enlargement in non-small-cell lung cancer

Background: The aim of this study was to elucidate the mediastinal lymphatic drainage of non-small-cell lung cancer (NSCLC). Methods: We retrospectively analyzed the frequency of enlarged mediastinal lymph node (LN) in 256 NSCLC patients with N2 or N3 diseases on CT scan, especially with respect to the location of primary tumor. Results: In 57 patients with right upper lobe (RUL) tumors, right lower paratracheal LN (89.5%) was the most commonly enlarged, followed by subcarinal LN (54.4%). In 61 patients with left upper lobe (LUL) tumors, left lower paratracheal (70.5%) and subaortic LNs (52.5%) were commonly enlarged. Subcarinal LN enlargement without ipsilateral superior mediastinal LN enlargement was rarely found in both upper lobe tumors; RUL 8.8%, LUL 6.6%. In patients with right or left lower lobe (RLL or LLL) tumors, the most commonly enlarged LN was subcarinal; 88.2%, 65.7%, respectively. In RLL tumors with both subcarinal and superior mediastinal LN enlargements, the frequency of ipsilateral superior mediastinal LN involvement was similar to that of bilateral superior mediastinal involvement. In LLL tumors with both subcarinal and superior mediastinal LN enlargements, bilateral superior mediastinal involvement was more frequent than ipseateral superior mediastinal involvement. Conclusion: The results of this study suggest that both upper lobe tumors are mainly drained directly to ipsilateral superior mediastinal LNs, and that both lower lobe lesions are drained to superior mediastinal LN via subcarinal LNs.