How to Define the Gastroesophageal Junction

Adenocarcinomas at the gastroesophageal junction (GEJ) are increasingly common worldwide. Current classifications, such as Siewert type II and Nishi, provide a foundation, but establishing a transparent and widely accepted framework could considerably enhance identification and treatment efforts. The recent definition proposed at the Kyoto international consensus conference defines the GEJ zone as the area 1 cm above and below the distal end of the palisade vessels, marking an important step forward. Research has shown that cardiac mucosa can be present from the fetal stage, with its extent often increasing due to conditions like gastroesophageal reflux and age. This phenomenon occurs as an adaptation to the microenvironment in response to, for example, reflux stimuli, and the stem cells responsible for cardiac-type mucosa are likely located in the gastric epithelium. However, intestinal metaplasia frequently arises from the stem cells located in the basal layer of squamous epithelium. CDX2 expression plays a significant role in the development of intestinal metaplasia. In the current classification of GEJ cancers, GEJ adenocarcinoma may represent a mix of what should be classified as esophageal adenocarcinoma (EAC) and non-GEJ gastric cancer. The Kyoto international consensus facilitates improved differentiation among EAC, GEJ cancer, and gastric adenocarcinoma. Furthermore, we will briefly discuss endoscopic treatment, chemotherapy, and surgical treatment for GEJ cancer. Looking ahead, the reclassification of GEJ cancers using the Kyoto international consensus, coupled with comprehensive molecular analyses of tumors, promises to yield valuable insights.