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

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.

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.

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.

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.