The histopathologic subtypes, determined according to the new IASLC/ATS/ERS classification of lung adenocarcinoma [36], were adenocarcinoma in preinvasive lesions in 17 patients (3.2%) and invasive adenocarcinoma in 481 patients (90.1%), with lepidic predominant, acinar predominant, papillary predominant, micropapillary predominant, and solid predominant with mucin production subtypes present in 111 (20.8%), 214 (40.1%), 29 (5.4%), 29 (5.4%), and 98 patients (18.4%), respectively, and variants of invasive adenocarcinoma in 36 patients (6.7%). This evidence concerns the gene MUC5AC and lung adenocarcinoma.