The biological Characteristics of Solid Components are Different between Part-Solid-Type and Solid-Type in Lung Adenocarcinoma
Numerous studies have been conducted to determine the clinical significance of the ground-glass opacity and solid-components in lung adenocarcinomas, however, few biological analyses of the two components have been carried out. This study was aimed at clarifying the biological characteristics of solid components in part-solid-type and solid-type lung adenocarcinomas. Data of a total of 112 cases of cT1b/cN0M0 lung adenocarcinoma treated by surgical resection were analyzed. We compared clinicopathological characteristics and prognosis between part-solid-type and solid-type tumors. In addition, we performed immunohistochemical analysis to determine the Ki-67 labeling index (LI), programmed cell death-1 ligand 1 (PD-L1) expression status, and CD8-positive tumor-infiltrating T lymphocyte (CD8+ TIL) count for the solid component of each tumor. Five-year recurrence-free survival (RFS) risks were significantly worse for patients with solid-type tumor than for those with part-solid-type tumor (51.7% vs. 83.2%; p < 0.001). The percentages of lymphovascular invasion, lymph node metastasis, high Ki-67 LI, and high PD-L1 expression were higher in the patient group with solid-type tumors. Univariate analysis identified Ki-67 LI, PD-L1 expression status, and CD8+ TIL count were identified as predictors of RFS in the entire subject population. Separate analyses in the two groups identified only the Ki-67 LI as an independent predictor of the RFS in the group with part-solid-type tumors, whereas in the group with solid-type tumors, the PD-L1 expression status and CD8+ TIL count were identified as independent predictors of the RFS. Clear differences in the biological characteristics of the solid-component were identified between part-solid-type and solid-type lung adenocarcinomas.