The more the micropapillary pattern in stage I lung adenocarcinoma, the worse the prognosis—a retrospective study on digitalized slides

Although the majority of lung adenocarcinomas show mixed pattern, only the predominant component is taken into account according to the novel classification. We evaluated the proportion of different patterns and their impact on overall survival (OS) and disease-free survival (DFS). Patterns were recorded according to predominance and their proportions were rated and calculated by objective area measuring on digitalized, annotated slides of resected stage I lung adenocarcinomas. Spearman’s rank correlation, Kaplan-Meier models and the log rank test were used for statistical evaluation. Two hundred forty-three stage I adenocarcinoma were included. Lepidic pattern is more frequent in tumours without recurrence (20 vs. 8%), and lepidic predominant tumours have favourable prognosis (OS 90.5%, DFS 89.4%), but proportions above 25% are not associated with improving outcome. Solid and micropapillary patterns are more frequent in patients with recurrence (48 vs. 5% and 13 vs. 4%) and predominance of each one is associated with unfavourable prognosis (OS 64.1%, DFS 56.3% and OS 28.1%, DFS 28.1%, respectively). Above 25%, a growing proportion of solid or micropapillary pattern is not associated with worsening prognosis. In contrast, tumours having micropapillary pattern as secondly predominant form a different intermediate group (OS 51.1%, DFS 57.8%). Our study was based on measured area of each growth pattern on all available slides digitalized. This is the most precise way of determining the size of each component from the material available. We propose using predominant and secondly predominant patterns for prognostic purposes, particularly in tumours having solid or micropapillary patterns.