Superior and Basal Segment Lung Cancers in the Lower Lobe Have Different Lymph Node Metastatic Pathways and Prognosis

Basal segment tumor metastasizes to the superior mediastinum mostly through the subcarinal node, whereas superior segment tumors often metastasize directly to the superior mediastinum without concomitant metastasis to the subcarinal node. Superior mediastinal dissection will be mandatory for accurate staging of superior segment tumors even when the subcarinal node is negative on frozen section. As for the prognosis among lower lobe N2 tumors, only in cases with basal segment tumor without superior mediastinal metastasis may long-term survival be expected.