[Prognostic study of visceral pleural invasion by pulmonary adenocarcinoma with tumor size ≤3 cm].

To evaluate the relationship between visceral pleural invasion (VPI) and other clinicopathological features in lung adenocarcinoma with tumor size ≤3 cm, and to investigate the impact of VPI on the patients' prognosis. The clinical and pathological features were retrospectively reviewed in 231 cases of lung adenocarcinoma with the largest diameter of tumor ≤3 cm, following complete resection and systemic lymphadenectomy. VPI was divided into three grades, PL0, PL1 and PL2 according to modified Hammar classification for lung cancer upon elastic fiber staining. Survival analysis was performed by Kaplan-Meier method, and the risk factors for prognosis were explored by Cox proportional hazards model. Patient prognosis was evaluated by progression-free survival (PFS) and overall survival (OS). In all 231 cases, the number of patients with VPI was 70 (30.3%), of which 61 cases were PL1 and 9 cases were PL2. The remaining 161 cases (69.7%) had no VPI (PL0). The tumor size (=0.003), histological grade (<0.01), the presence of solid component (=0.001) and micropapillary component (=0.009), N stage (<0.01) and TNM stage (<0.01) were significantly correlated with VPI. Patients with VPI had significantly shorter PFS and OS than those without VPI (<0.01). There were significant differences in PFS and OS between patients with different VPI levels (<0.01). Cox multivariate regression analysis showed that VPI was not an independent prognostic factor, whereas PL2 was an independent prognostic factor for PFS (=0.007), but not an independent prognostic factor for OS (=0.052). For patients with lung adenocarcinoma of tumor size ≤3 cm, VPI is related to poor prognosis; However, only PL2 is an independent prognostic factor for PFS. It may be not necessary to separate PL0 and PL1 status in smaller lung adenocarcinomas. Therefore, the definition of VPI may need further modification through large cohort studies.