SOX2 and squamous cell lung carcinoma: SOX2 has been shown to be highly expressed in approximately 90 % of pulmonary squamous cell carcinoma and to a lesser extent in adenocarcinoma [16] and several studies have previously identified SOX2 gene amplifications in lung squamous cell carcinomas with reported frequencies from 20 % to 60 % [13, 15, 33–36].