Correlations Between the EGFR Mutation Status and Clinicopathological Features of Clinical Stage I Lung Adenocarcinoma

Advanced lung cancers with epidermal growth factor receptor (EGFR) exon 19 deletions (Ex19s) and EGFR exon 21 L858R point mutations (Ex21s) exhibit different clinical behavior. However, these differences are unclear in resectable primary lung tumors. The clinicopathological features of 88 (20.9%) Ex19, 124 (29.4%) Ex21, and 198 (46.9%) EGFR wild-type (Wt) clinical stage I primary adenocarcinomas resected between January 1, 2012 and October 31, 2014 were compared by using Chi-square tests, residual error analysis, analysis of variance, and Tukey tests. Ex21 lesions occurred more frequently in women and never-smokers and had a higher tumor disappearance rate (TDR: 59.6% vs 43.9%; P<0.001) and lower maximum standardized uptake value (maxSUV: 2.0 vs 3.5; P<0.01) than Wt lesions; Ex19 lesions had intermediate values (52.8% and 2.6). There was a low frequency of vascular invasion in Ex21 lesions (12.1%; P<0.05) and a high frequency in Wt lesions (22.7%; P<0.05). Most Ex19 lesions were intermediate-grade adenocarcinoma (lepidic, acinar, and papillary predominant: 73.9%; P<0.05). Wt and Ex21 lesions were predominately high-grade (micropapillary or solid predominant, mucinous variant) and low-grade (adenocarcinoma in situ and minimally invasive adenocarcinoma) adenocarcinoma, respectively. Wt lesions had smaller lepidic components (42.1% vs 56.3%; P<0.001) and larger papillary and solid components (papillary: 15.5% vs 9.0%; P<0.05; solid: 13.2% vs 3.2%; P<0.001) than Ex21 lesions. Most Ex19 lesions had intermediate component rates. Most Ex21 lesions were low-grade adenocarcinoma with lepidic growth patterns. Wt high-grade adenocarcinomas included solid and papillary components with vascular invasion. Ex19 lesions were intermediate grade between Ex21 and Wt.