The epidermal growth factor receptor (EGFR) mutation status has become one of the most important factors in the treatment of non-small cell lung cancer. However, the relationship between EGFR mutation and the histologic subtype of lung adenocarcinoma remains to be fully elucidated. We examined the relationship between the predominant subtype of adenocarcinoma and the prognosis and investigated the correlation between a new subtype of adenocarcinoma and EGFR mutations. This study included 182 patients with adenocarcinoma who underwent complete resection. The rate of EGFR mutation-positive patients was significantly higher among female patients, never smokers, patients with small tumors (< 3 cm in size), patients with well-differentiated tumors, and patients with a pStage I classification. The rates of adenocarcinoma in situ (AIS), minimally invasive adenocarcinoma (MIA), and lepidic-predominant subtype were high in male EGFR mutation-positive patients. The prevalence of the acinar and papillary-predominant subtypes was high among EGFR mutation-positive female patients, as was AIS, MIA, and the lepidic-predominant subtype. The progression-free survival (PFS) of the EGFR mutation-positive patients was significantly better than that of the EGFR mutation-negative patients (75.8 vs 67.1%, p = 0.03). However, the multivariate analysis of clinicopathologic and histologic factors did not reveal the prognostic impact of the EGFR mutation status on PFS. The overall survival (OS) of the EGFR mutation-positive patients was significantly better than that of the EGFR mutation-negative patients (93.7 vs 63.4%, p < 0.01). However, in the multivariate analysis the EGFR mutation status was not significantly associated with OS.
Keywords: EGFR mutation; Histologic subtype; Lung adenocarcinoma; Prognosis.