KRAS and adenoma: Conversely to KRAS, the loss of the APC gene, located on chromosome 5 and correlated with the nuclear localization of oncoprotein β-catenin [54], is more frequent in NG-LSTs rather than G-LSTs [22,45], while several studies show a lower frequency of APC mutations in LSTs compared to polypoid lesions, suggesting a different way undertaken by flat-type adenomas for neoplastic transformation.