Prognostic impact according to the proportion of the lepidic subtype in stage IA acinar‐predominant lung adenocarcinoma

BACKGROUND: Adenocarcinoma is the most common type of lung cancer and most adenocarcinomas have heterogeneous subtypes. Acinar‐predominant adenocarcinoma is the most common. This study aimed to identify the prognostic impact of other mixed histological subtypes in acinar‐predominant lung adenocarcinoma. METHODS: The medical records of patients with pathological stage IA acinar‐predominant lung adenocarcinoma between January 2010 and April 2016 were reviewed. The patients were divided into two groups according to the proportion of the lepidic subtype, with a cutoff value of 20%, and prognostic factors were analyzed. RESULTS: A total of 215 patients with stage IA acinar‐predominant adenocarcinoma were reviewed. The 20% or more lepidic subtype group had a low value of SUVmax (p = 0.001), good differentiation (p < 0.001) and a low incidence of the solid histological subtype (p = 0.016). Recurrence was significantly lower in the 20% or more lepidic subtype group (p = 0.008). The disease‐free survival (p = 0.007) and overall survival (p = 0.046) were significantly different between the two groups. Multivariate analysis showed that lymphovascular invasion (p = 0.006) and no or less than 20% lepidic subtype (p = 0.036) were significant prognostic factors for disease‐free survival. CONCLUSIONS: The lepidic proportion may be useful to predict recurrence in acinar‐predominant stage IA lung adenocarcinoma.