Visceral Pleural Invasion Is a Significant Prognostic Factor in Patients with Partly Solid Lung Adenocarcinoma Sized 30 mm or Smaller

Background This study analyzed the impact of visceral pleural invasion (VPI) on the disease-free survival (DFS) of patients with partly solid pulmonary adenocarcinoma sized 30 mm or smaller. Method This is a retrospective study of 147 patients with surgically resected pathologic N0 pulmonary adenocarcinoma that had a partly solid appearance on preoperative computed tomography. All patients presented with tumors of size 30 mm or smaller. The DFS rate was estimated using Kaplan–Meier method. A multivariate analysis for prognostic factors was performed using the Cox proportional hazards regression model. Results VPI was found in 36 patients. The 5-year DFS in 111 patients without VPI (97.6%) was significantly higher than that in 36 patients with VPI (63%) (p < 0.0001). Univariate analysis revealed three significant poor prognostic predictors: the presence of VPI, the presence of lymphovascular invasion, and the size of the solid component on computed tomography (>20, ≤30 mm). According to the multivariate analysis, VPI was found to be a significant poor prognostic predictor (hazard ratio for DFS = 7.31, 95% confidence interval = 1.444–37.014, p = 0.016). Conclusion VPI is a significant predictor of poor prognosis for small-sized (≤30 mm) partly solid lung adenocarcinoma. Therefore, upstaging of the T factor from T1 to T2 on the basis of VPI as described by the TNM staging system is mandatory regardless of ground-glass opacity in small lung adenocarcinoma.