Lepidic and micropapillary growth pattern and expression of Napsin A can stratify patients of stage I lung adenocarcinoma into different prognostic subgroup.

Histologic categories and related growth pattern proposed by IASLC/ATS/ERS classification has been reported to be prognostically important in lung adenocarcinoma. Thyroid transcription factor-1 (TTF1) and Napsin A have been investigated as potential prognostic parameters with conflicting results. A total of 211 cases with stage I lung adenocarcinoma were analyzed according to the IASLC/ATS/ERS classification with slight modifications. Expression levels of TTF1 and Napsin A were evaluated by immunohistochemistry. In univariate analyses, we found female sex (p=0.009), lepidic growth pattern (P=0.011) and lack of micropapillary pattern (P=0.048) were favorable predictor significantly associated with disease-free survival (DFS). Lack of mitosis (P=0.044) and Napsin A expression (P=0.031) were favorable predictors for overall survival (OS). Tumors with a maximum diameter≤2 cm had both longer DFS (P=0.008) and OS (P=0.020). Negative TTF1 expression indicated increased risk of death, but failure in statistical significance (P=0.215). After multivariate analysis, histologic subtype, tumor size and gender were identified as independent predictor for DFS (RR: 0.343, 3.697, 0.494; P=0.006, 0.029, 0.019), no feature was found as an independent predictor for overall survival (P>0.05). To conclude, lepidic growth pattern, female sex and tumor size≤2 cm are independent favorable predictors for tumor recurrence, tumors with more than 5% percentage of lepidic growth pattern will have a better prognosis than absence, in early-stage lung adenocarcinoma.