["Neosquamous epithelium (NSE) can arise within Barrett's esophagus as a consequence of medical or surgical acid reduction therapy, as well as after endoscopic ablation. Morphologic studies have suggested that NSE can develop from adjacent squamous epithelium, submucosal gland ducts, or multipotent progenitor cell(s) that can give rise to either squamous or Barrett's epithelium, depending on the luminal environment. The cells responsible for Barrett's epithelium self-renewal are frequently mutated during neoplastic progression. If NSE arises from the same cells that self-renew the Barrett's epithelium, the two tissues should be clonally related and share genetic alterations; if NSE does not originate in the self-renewing Barrett's, NSE and Barrett's esophagus should be genetically independent.", "We isolated islands of NSE and the surrounding Barrett's epithelium from 20 patients by microdissection and evaluated each tissue for genetic alterations in exon 2 of CDKN2A or exons 5 to 9 of the TP53 gene. Nine patients had p16 mutations and 11 had TP53 mutations within the Barrett's epithelium.", "In 1 of 20 patients, a focus of NSE had a 146 bp deletion in p16 identical to that found in surrounding Barrett's epithelium. The NSE in the remaining 19 patients was wild-type for p16 or TP53."] Does neosquamous epithelium typically arise from Barrett 's epithelium?