Dilemmas in definition and classification of adenocarcinoma of esophagogastric junction: from history to current status

Abstract

In recent years, adenocarcinoma of esophagogastric junction (AEG) has received increased attention from the academic community. However, the esophagogastric junction (EGJ) straddles two anatomical regions: the thoracic cavity and the abdominal cavity. The histological features of the EGJ are different from those of the esophagus and stomach. There are general disagreements among the related disciplines regarding the definition and classification of AEG. By summarizing the views of different disciplines, including endoscopy, radiography, and pathology, a more comprehensive definition of the EGJ was formulated in the Japanese Classification of Gastric Carcinoma (the 15th edition), and the principle of endoscopic diagnostic priority was established. In recent years, with the development of physiological and anatomical studies, the EGJ has gradually expanded conceptually into a complex functional anatomical region covering the distal esophagus to the proximal stomach. The venous and lymphatic vessels in the EGJ are characterized by bidirectional flow, which is an important anatomical basis for the invasion and metastasis patterns of tumors in this region. The clinical practice of EGJ cancer has been promoted by the creation of Nishi and Siewert classification systems. With the support of a series of clinical studies for its scientificity and effectiveness, the Siewert classification is widely accepted by the international community, and successively introduced into major international practice guidelines. In general, the staging and management of Siewert Ⅰ and Ⅱ AEG are recommended as esophageal cancer, while Siewert Ⅲ AEG is recommended for gastric cancer. However, in the Japanese guidelines for the treatment of esophageal and gastric cancers, the Nishi classification is still used to define and classify EGJ cancer. Recent year, a Chinese consensus on the surgical treatment of AEG was formulated by multidisciplinary experts. The main controversies were summarized in the consensus, and proposals that incorporate the domestic situation were also presented. At present, only by returning to the basic anatomical and physiological perspectives, strengthening multidisciplinary communication and cooperation, and with the help of emerging bioinformatics, digital, and material technology, can it be possible to get out of the dilemma faced by traditional AEG classification and staging system.