Analysis of the lymph node metastasis distribution in patients with invasive resectable non-small cell lung cancer.

Background: The current standard for the surgical management of lung cancer involves anatomic lung resection combined with systemic lymph node dissection/sampling. The purpose of this study was to investigate the patterns of pathological lymph nodes in invasive non-small cell lung cancer (NSCLC), explore the occurrence in lymph node metastasis (LNM), and provide recommendations for optimal lymph node resection/sampling in lung cancer operation.

Methods: There were 1,678 patients with NSCLC who underwent lobectomy between 2018 and 2021 at the Taizhou Hospital of Zhejiang Province were reviewed retrospectively. The location and incidence of LNM and postoperative pathological findings were studied. We analysed the metastasis rates of lymph node dissection stations using Pearson's χ² and Fisher's exact tests.

Results: There were 1,308 patients assessed as eligible and included in the study. The median number of lymph nodes cleared in the cohort was 11.2±5.1. In patients with lung adenocarcinoma, the rate of LNM was significantly higher in central than in peripheral lung cancer, especially in 2R/2L, L7, L9, L10, L11, and L12. Lung cancer patients with tumors ≤1 cm had no N2 lymph node metastases but few (2/191, 1.1%) N1 lymph node metastases. The likelihood of N2 metastasis increased (T1a, 0%, 0/191; T1b 3.5%, 22/625; T1c, 5.6%, 14/249; T2 and above, 18.9%, 46/243) with increasing tumor diameter. Thirty-four patients with stage N2 lung adenocarcinoma and 1-3 cm tumors displayed lobe-specific lymph node metastases in the mediastinum. In patients diagnosed with squamous cell carcinoma, no significant differences were observed in mediastinal LNM across various parameters (central versus peripheral location, tumor site, and tumor size).

Conclusions: Our study proposes recommendations for lymph node resection according to the pathological type of lung cancer, tumor location, lung lobes affected and tumor size, which may provide a certain reference value for the clinical work.