EGFR and squamous cell carcinoma: The frequency of EGFR mutations, either in exon 19 or exon 21, was higher in women than in men (p=0.015; p<0.0005), in adenocarcinoma than in squamous cell carcinoma (p<0.0005; p<0.0005), and in the non-smokers than in smokers (p=0.031; p=0.002).