Supplementary Material for: The Origin of Epithelium with Low-Grade Atypia in Early Gastric Cancer

<b><i>Introduction:</i></b> <i>Helicobacter pylori</i> (HP) infection causes chronic inflammation and atrophy of the gastric mucosa and thus a high risk of gastric cancer (GC). With the increasing success of HP infection treatment, a larger number of GCs that develop after eradication can be assessed. Several studies have shown that epithelium with low-grade atypia (ELA) is a frequent characteristic of these GCs, but the origin of this condition is unknown. In this study, we compared the mucin phenotype, cellular proliferation, and p53 staining in ELA and cancerous tissues obtained from patients with GC with and without HP eradication. <b><i>Methods:</i></b> The study population consisted of 23 patients with GC that developed after successful HP eradication therapy (eradicated group) and 24 patients with GC and HP infection (infected group). The prevalence of ELA was determined by hematoxylin and eosin staining. Tumor tissue and ELA samples were further analyzed by immunohistochemical staining for Muc5AC, Muc2, p53, and Ki-67. <b><i>Results:</i></b> The ELA coverage rate was significantly higher in the eradicated group than in the infected group. Gastric-type mucin was frequently expressed by the ELA, and the mucin phenotypes of ELA and cancerous areas differed in 75% of cases. The Ki-67 labeling index was consistently lower in ELA than in the cancerous mucosa. Fourteen of 21 (66.7%) cancerous lesions, but only 3 ELA samples, were p53-positive. <b><i>Conclusion:</i></b> In most cases, ELA on the surfaces of GCs seems to have originated from normal gastric cells, not from cancer cells.