In this study, firstly, the immunohistochemical mucin-stainings and p53-overexpression, and secondary, the replication error (RER) of the microsatellite (MS) in chromosome 17 related p53 gene of the super-minute sized differentiated adenocarcinoma lesions in the human stomachs, whose definition was described below, were investigated, because the carcinoma cells were positive p53 in all carcinoma lesions in the current study, and the new findings on histogenesis of gastric adenocarcinoma were revealed. The gene discussed is MUC5AC; the disease is carcinoma.