Many publications focusing on the background or original mucosa of Barrett adenocarcinoma have maintained that adenocarcinoma arises in intestinal-type mucosa with goblet cells in the columnar-lined esophagus, and this has become a central dogma. The mucosa on each side of a series of 141 minute esophageal adenocarcinomas (almost all of which were mucosal carcinomas) resected by endoscopic mucosal resection was recorded as the background mucosa. All 141 cases had endoscopic evidence of an esophageal origin, and for 113 of them, histologic evidence of an esophageal origin was also available. The mucosae were classified into 4 types--squamous, cardiac, fundic, and intestinal--based on routine histology and immunohistochemical staining. The present joint pathologic examination of the background mucosa of Barrett adenocarcinoma conducted by Japanese and German pathologists and gastroenterologists found that more than 70% of primary small adenocarcinomas (<2 cm) of the esophagus were adjacent to cardiac/fundic-type rather than intestinal-type mucosa. Moreover, intestinal metaplasia was not observed in any areas of the endoscopic mucosal resection specimens in 64 (56.6%) of the 113 cases. In other words, there was no evidence to support the previously held view that Barrett adenocarcinoma is nearly always accompanied and preceded by intestinal-type mucosa. Our study has demonstrated a close relationship between esophageal adenocarcinoma and cardiac-type mucosa. Therefore, it is not proven histogenetically that the background mucosa of esophageal adenocarcinoma is the intestinal type. Also, it seems better to define Barrett esophagus as metaplastic columnar-lined esophagus alone, without requiring the presence of goblet cells, in accordance with histogenetic and practical standpoints.