Antropyloric Mass Location
An antropyloric mass is purely gastric and does not reach the gastroesophageal junction (GEJ). The antropyloric region is anatomically confined to the distal stomach between the antrum and pylorus, which is located more than 2 cm below the GEJ 1.
Anatomical Boundaries
The antropyloric region is located in the distal one-third of the stomach, specifically between the gastric antrum and the pylorus, which represents the most distal portion of the stomach before the duodenum 1.
The gastroesophageal junction is located approximately 40 cm from the incisors, marking the transition from esophageal to gastric mucosa, and is anatomically distant from the antropyloric region 2.
For a mass to involve the GEJ, its epicenter must be within 1 cm proximal and 2 cm distal to the anatomic GEJ (classified as AEG type II), or more than 2 cm below the GEJ (AEG type III) 1.
Classification Framework
The Siewert classification system clearly delineates tumor locations relative to the GEJ 1:
- Type I (AEG I): Epicenter >1 cm above the anatomic GEJ (distal esophageal)
- Type II (AEG II): Epicenter within 1 cm proximal and 2 cm distal to the GEJ (true cardia)
- Type III (AEG III): Epicenter >2 cm below the GEJ (subcardiac gastric carcinoma that may infiltrate the GEJ from below)
An antropyloric mass would be classified as a distal gastric tumor, not an esophagogastric junctional tumor, unless there is extensive proximal extension 1.
Clinical Implications for Treatment Planning
Distal antrum/pylorus primaries require inclusion of the pancreatic head and duodenum in radiation fields only if the gross lesion extends to the gastroduodenal junction 1.
Nodal areas at risk for antropyloric tumors include perigastric, suprapancreatic, celiac, porta hepatic, and pancreaticoduodenal lymph nodes—notably different from the paraesophageal nodes involved with GEJ tumors 1.
Surgical approach for distal tumors is subtotal gastrectomy, whereas proximal tumors or GEJ involvement requires total gastrectomy or esophagogastrectomy 1.
Critical Distinction
The key anatomical fact is that the antropyloric region is separated from the GEJ by the entire proximal stomach (cardia and fundus) and body of the stomach. A mass would need to demonstrate extensive proximal extension through multiple gastric anatomical zones to reach the GEJ, at which point it would be reclassified based on the location of its epicenter or dominant tumor mass 1.