Impact of minimal solid and micropapillary components on invasive lung adenocarcinoma recurrence.

Background: The specific impacts of solid and micropapillary components on prognosis in lung adenocarcinoma remain unclear. Herein, we elucidated their distinct contributions to lung adenocarcinoma recurrence.

Materials And Methods: Lung adenocarcinoma was classified into solid and micropapillary absent (S-M-); solid absent, micropapillary present (S-M+); micropapillary absent, solid present (S + M-); and solid and micropapillary present (S + M+). Cumulative incidence of recurrence (CIR) was calculated using competing risk analysis.

Results: Of 994 adenocarcinomas, 650 (65.4%) were classified as S-M-; 152 (15.3%), S-M+; 148 (14.9%), S + M-; and 44 (4.4%), S + M+. In total, 168 (16.9%) patients had recurrence; 16 (1.6%) died from other causes. S-M- had significantly lower CIR than other groups (S-M- vs. S-M+: P < 0.001, S-M- vs. S + M-: P < 0.001, S-M- vs. S + M+: P < 0.001); S + M- had significantly higher CIR than S-M+ (P = 0.002). These differences remained significant in multivariable analysis. In stage IA, S-M- had significantly lower CIR than other groups (S-M- vs. S-M+: P = 0.006, S-M- vs. S + M-: P < 0.001, S-M- vs. S + M+: P < 0.001); S + M- and S + M+ had significantly higher CIR than S-M+ (P = 0.005, P = 0.008, respectively). These differences remained significant in multivariable analysis. CIR was not significantly different between S + M- and S-M+ subgroups.

Conclusions: The presence of solid or micropapillary component (≥1%) was an independent risk factor for CIR; patients with solid component alone had a higher CIR than those with micropapillary component alone. In IA lung adenocarcinoma, patients with both solid and micropapillary components had a higher CIR than those with micropapillary component alone; the proportion of solid or micropapillary component was not associated with CIR.