KRAS and carcinoma: Vogelstein et al (1988) proposed that Ki-ras mutation is an early event in the adenoma–carcinoma sequence with Ki-ras mutational status possibly determining development of an exophytic polypoid adenoma. Our results suggest that in contrast a Ki-ras mutation might not be present in the NPG carcinoma pathway even when the lesion is advanced. Our previous and present studies indicate that Ki-ras mutation is not related to genetic progression in morphologically distinct nonpolypoid lesions containing NPG carcinomas.