Lymph Node Metastasis and Recurrence Patterns in Clinical Stage IA Lower-Lobe Non-Small Cell Lung Cancer: Toward an Optimal Surgical Strategy for Superior Segment (S6) Tumors.

PURPOSE: The superior segment (S6) may differ from the basal segments (BSs) in lymphatic spread, affecting surgical strategy and mediastinal lymph node dissection (LND). We aimed to define lymphatic spread patterns and to guide surgical strategy in S6 non-small cell lung cancer (NSCLC). METHODS: We reviewed 375 patients with cT1a-cT1c N0 lower-lobe NSCLC (S6, 168; BS, 207) who underwent segmentectomy or lobectomy (2012-2024). We analyzed nodal metastasis and recurrence by station. RESULTS: Segmentectomy was more frequent in S6 than in BS. pN1 and pN2 incidence was 8.3% and 2.4% in S6 and 4.3% and 6.8% in BS, respectively. In S6, pN2 metastases were single-station with N1, with no inferior mediastinal involvement. S6 nodal recurrences were confined to #4L/#4R and occurred outside the LND field. In BS, skip pN2 was more frequent and nodal recurrences occurred at #7 within the field. CONCLUSION: In clinical stage IA S6 NSCLC, nodal events occurred in the superior mediastinal stations. All pN2 were single-station with N1, and all nodal recurrences occurred after lobe-specific mediastinal LND. Management should follow intraoperative N1 assessment: if negative, S6 segmentectomy without mediastinal LND; if positive, lobectomy with superior mediastinal and subcarinal LND, omitting inferior mediastinal nodes unless specifically suspected.