APOBEC1 and Barrett esophagus: We do not know yet at which stage in EAC oncogenesis AID/APOBECs exert their mutagenic potential; however, since Barrett’s esophagus can be regarded as a precursor of EAC, and since genomic alterations of EAC are already seen in Barrett’s esophagus [49-52], we surmise that AID/APOBECs play a role at an early stage, even though further studies will be needed to assess the specific contribution of APOBEC1 compared with other AID/APOBECs.