A lone, heterozygous oncogenic K-Ras mutation in a large number of cells can also lead to the development of lung ADs, although only a very small number of these cells in a specific cellular context are transformed by oncogenic K-Ras [48], indicating that certain spontaneously occurring rare molecular events are involved in the development of K-Ras-activated lung cancer. The gene discussed is KRAS; the disease is lung cancer.