Mucin expression and proliferating cell index of esophageal Barrett's adenocarcinoma

Barrett's esophagus is a premalignant condition associated with gastroesophageal reflux disease, and consists of mucosa with a metaplastic columnar epithelium (specialized columnar epithelium). In this study, we examined the expression of mucin and the Ki-67 labeling index (LI) in 15 cases of esophageal Barrett's adenocarcinoma, and clarified the significance of incomplete intestinal metaplasia of Barrett's mucosa as a premalignant lesion. Gastric mucin (MUC5AC, HGM, and/or MUC6) was detected in 93.3% of the adenocarcinomas, while MUC2 and CD10 (markers of intestinal phenotypes) were detected in 73.3% and 46.2%, respectively. The Ki-67 LI was 34.1% in Barrett's adenocarcinoma. In all cases, gastric mucin was found in the non-neoplastic Barrett's mucosa around the adenocarcinoma. MUC2 was detected in 86.7% of proximal non-neoplastic mucosa and 100% of distal non-neoplastic mucosa, while CD10 was found in 20.0% of proximal non-neoplastic mucosa and 40.0% of distal non-neoplastic mucosa of Barrett's adenocarcinoma. In conclusion, Barrett's esophageal mucosa with intestinal metaplasia and a high Ki-67 LI is suggested to be more important as a premalignant lesion, and predominantly found in the proximal rather than distal region of Barrett's esophagus.