Prognostic significance of micropapillary and solid patterns in stage IA lung adenocarcinoma

To evaluate the value of the non-predominant micropapillary and solid patterns in prognosis of lung adenocarcinoma.

Totally 422 patients diagnosed with stage IA lung adenocarcinomas were included, and all their slides were reviewed. We compared clinicopathological characteristics and survival outcomes between MP- & SD- (both micropapillary and solid component were absent), MP+/SD+ (either micropapillary or solid component was present, but the single or combined percentage of the MP and SD was not greater than 50%) and MPp/SDp (either micropapillary or solid or the combined percentage of these two components was great than 50%).

Patients with MP- & SD- had smaller tumor size (P=0.012) and lower spread through air spaces rates (P<0.001). Patients with MP- & SD- had significantly better 5-year recurrence free survival than MP+/SD+ (91% versus 70%, P<0.001) and MPp/SDp (91% versus 56%, P<0.001). The difference of RFS between MP+/SD+ subgroup and MPp/SDp subgroup was not significant (P=0.177). In the multivariate analysis, patients with MP- & SD- had a better recurrence free survival than the other two groups (versus: MP+/SD+, HR, 3.198; 95% CI, 1.537-6.653; P=0.002; versus MPp/SDp: HR, 4.981; 95% CI, 2.266-10.950; P<0.001).

The presence of micropapillary or solid patterns, even not predominant, was a risk factor for predicting poor recurrence free survival in very early stage lung adenocarcinoma.