In this study, we argue that the basic clonal unit that makes up the Barrett's segment is at the level of the gland. There is expansion of this clonal unit, the gland, by fission, and there is evidence that the Barrett's segment is itself a clonal proliferation. Barrett's esophagus arises from both goblet cell-containing metaplasia and non-goblet cell-containing metaplasia and may arise from a stable clone, but the genomic changes occurring are subject to selection, usually with little or no evolution, appearing indolent from the evolutionary perspective. Genomic changes leading to dysplastic phenotypes are selected, but without any single clone predominating within the segment.
Keywords: Barrett’s esophagus; Carcinoma; Clonal evolution.