Necessity of systematic lymph node dissection in early-stage pure solid lung cancer adjacent to the mediastinum.

Pure solid lung cancer is associated with higher lymph node metastasis rates, therefore identifying the risk factors and metastatic patterns of lymph node involvement in early-stage pure solid lung cancer is a critical research topic. We retrospectively collected preoperative Computed Tomography (CT) imaging and postoperative pathological data of patients with pure solid lung cancer from 2021 to 2025 to investigate the risk factors and patterns of lymph node metastasis. Among 8718 patients, 104 with ≤ 2 cm pure solid lung cancer were analyzed, with a lymph node metastasis rate of 20.19% (21/104). Risk factors included mediastinal proximity (Odds Ratio (OR) = 11.83, 95% CI 2.18-64.32, p = 0.004) and ALK-positivity (OR = 15.13, 95% CI 1.68-136.01, p = 0.015). In 76 clinical stage IA patients, the metastasis rate was 15.79% (12/76). Risk factors were mediastinal proximity (OR = 11.53, 95% CI 1.13-118.01, p = 0.039), and ALK-positivity (OR = 33.74, 95% CI 3.02-376.65, p = 0.004). Upper lobe pure solid lung cancers tended to metastasize to the superior mediastinal lymph nodes (p = 0.011). Mediastinal proximity and ALK-positivity were independent risk factor of lymph node metastasis in pure solid lung cancer. Systematic lymph node dissection is proper for mediastinal-adjacent pure solid lung cancer.