For example, the described frequency of positive MUC5AC immunostaining ranged from 29% to 100% in nonsmall-cell lung cancer,23,24 15% to 100% in lung adenocarcinoma,13,25 25% to 85% in gastric cancer,26,27 0% to 100% in ovarian carcinoma,9,28 28% to 80% of the ampulla Vater,29,30 or 14% to 54% in cervical carcinomas.12,31 Technical factors, such as staining protocols and antibodies used, different definitions of thresholds to determine positivity, as well as possible selection bias with respect to the analyzed tumors may have caused these discrepancies. This evidence concerns the gene MUC5AC and lung adenocarcinoma.