Gastroesophageal junction tissue (GEJ) (GEJ)

The gastroesophageal junction (GEJ) is the anatomical transition zone where the distal esophagus meets the cardia of the stomach (StatPearls, 2023). It functions as a physiological valve, primarily regulated by the lower esophageal sphincter, to allow food passage while preventing the retrograde flow of acidic gastric contents. This region is clinically significant as a primary site for pathologies such as gastroesophageal reflux disease (GERD) and Barrett's esophagus, which can progress to GEJ adenocarcinoma (NCI, 2024). In oncology, the GEJ is treated as a distinct entity for staging and therapeutic selection, often involving molecular targets like HER2 or PD-L1 (PubMed, 2022). Because it is a complex tissue structure rather than a single protein or receptor, it is not classified as a molecular therapeutic target itself. Instead, it serves as the microenvironment where various pharmacological agents, such as proton pump inhibitors or monoclonal antibodies, exert their effects on specific molecular pathways.

Other names

GE junctionEsophagogastric junctionEGJZ-lineCardioesophageal junction

Not applicable; the GEJ is an anatomical location and not a single molecular target. Drugs acting at this site target specific receptors (e.g., HER2) or physiological processes (e.g., gastric acid secretion).