Numerous studies have reported that K-RAS mutation, the genetic alteration most frequently detected in lung cancer, is an early event responsible for the development of lung adenoma.10, 11, 12, 13, 14 However, the p14ARF–p53 pathway effectively defends the cell against aberrant oncogene activation.15, 16, 17 Therefore, it is important to determine whether one or more hidden tumor suppressors are inactivated in lung adenomas, or instead the p14ARF–p53 pathway simply provides an incomplete defense against oncogenic K-RAS-induced tumorigenesis. The gene discussed is KRAS; the disease is neoplasm.