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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.