KRAS and neoplasm: In contrast, Kras;Lkb1 (KL) mice develop more aggressive tumours with an expanded histopathology spectrum 14, 16, and we recently showed that histotype spectra are dependent on the cell of origin: whereas alveolar progenitors predominantly lead to the formation of papillary AC, bronchiolar progenitors predominantly lead to the formation of adenosquamous carcinoma (ASC) and occasional mucinous or acinar AC 22.