What is the difference between the true gastroesophageal (GE) junction and the gastroesophageal (GE) junction?

Understanding the True GE Junction versus the Clinical GE Junction

The "true" gastroesophageal (GE) junction is a histopathological definition representing the border between esophageal and gastric muscles (specifically, the proximal limit of gastric oxyntic mucosa), while the clinical "GE junction" refers to endoscopic landmarks used during procedures—most commonly the proximal margin of the gastric folds. These two definitions do not always coincide, and this discrepancy has critical implications for diagnosing Barrett's esophagus and classifying GE junction tumors.

The True (Histopathological) GE Junction

The true anatomic GE junction is defined histologically as the border between esophageal and gastric muscles, specifically marked by the proximal limit of gastric oxyntic mucosa. 1

Key histological markers include:

• Presence of esophageal submucosal glands: These glands are found in the esophagus but never under gastric oxyntic mucosa, making them a definitive marker of esophageal tissue 2
• The transition from esophageal to gastric muscle layers: This represents the actual anatomic boundary 1
• Native esophageal structures: Including submucosal gland ducts, multi-layered epithelium, or squamous islands, though these are present in only 10-15% of biopsy samples 1

A critical finding from surgical specimen studies shows that up to 2.05 cm of what appears endoscopically as "stomach" (the saccular region with rugal folds) actually contains esophageal submucosal glands and therefore represents reflux-damaged distal esophagus, not true stomach. 2 This means the endoscopic landmarks systematically misidentify the true GE junction by placing it too distally.

The Clinical (Endoscopic) GE Junction

For practical clinical purposes, the GE junction is identified endoscopically using the proximal margin of the longitudinal gastric folds with minimal air insufflation, which has a reliability coefficient of 0.88. 1, 3

Alternative endoscopic landmarks include:

• The distal end of the longitudinal palisading vessels in the lower esophagus, though this has poor reproducibility (κ = 0.14) 1, 3
• The horizontal level of the angle of His on barium studies 1
• The level of macroscopic caliber change between esophagus and stomach on resected specimens 1

Critical Clinical Implications

For Barrett's Esophagus Diagnosis

Barrett's esophagus requires columnar epithelium to be clearly visible ≥1 cm above the endoscopically defined GE junction (using gastric folds), not the true histological junction. 1, 3 This creates a systematic bias where:

• Short segments of columnar mucosa (cardiac-type or oxyntocardiac mucosa) located between the endoscopic GE junction and the true histological junction may actually represent reflux-damaged esophagus, not gastric cardia 4, 5, 2
• The clinical definition accepts that some "gastric cardia" is actually metaplastic esophagus, but this cannot be distinguished without surgical specimens 1, 4, 5

For GE Junction Tumor Classification

The Japanese Classification defines the EGJ area as extending 2 cm above to 2 cm below the esophagogastric junction, with the EGJ defined as the border between esophageal and gastric muscles. 1 Tumors with their epicenter in this 4 cm zone are classified as EGJ carcinomas using the symbols E (proximal 2 cm) and G (distal 2 cm), with dominant invasion area listed first (E, EG, E=G, GE, or G). 1

Important Distinction: GE Junction vs. Squamocolumnar Junction

The squamocolumnar junction (SCJ) does NOT coincide with the GE junction in most adults, particularly those with GERD. 1 The SCJ represents where squamous epithelium transitions to columnar epithelium and is typically displaced proximally in patients with reflux, creating the columnar-lined segment that defines Barrett's esophagus. 1, 4, 5

Common Pitfalls to Avoid

• Do not use the SCJ to identify the GE junction—these are separate landmarks that diverge in the presence of columnar metaplasia 1
• Do not diagnose Barrett's esophagus based on irregular Z-line alone (tongues <1 cm)—this does not meet the ≥1 cm threshold above the GE junction 1, 3
• Recognize that "gastric cardia" biopsies may actually represent esophageal tissue when obtained near the endoscopic GE junction, as the true junction may be up to 2 cm more distal 2
• Understand that the presence of palisading vessels has poor inter-observer reliability (κ = 0.14) and should not be the primary landmark 3