History of the lymph node numbering system in the Japanese Classification of Gastric Carcinoma since 1962.

The Japanese Classification of Gastric Carcinoma was established by the Japanese Research Society for Gastric Cancer in 1962. The latest 15th edition was published in 2017. One of its main features is that lymph nodes are numbered as stations. The number of groups has increased from 16 to 36 in 55 years. Seven groups (nos. 1, 2, 5, 7, 9, 10, and 15) were retained from the original classification. Nine groups (nos. 3, 4, 6, 8, 11, 12, 13, 14, and 16) were sub-divided into two or more groups. Furthermore, seven groups (nos. 17, 18, 19, 20, 110, 111, and 112) were added in the 6th, 11th, and 12th editions. This numbering system helps surgeons recognize the exact lymph nodes that need to be dissected. However, the numbering system has become extremely complicated. It is necessary to organize the historical background of each lymph node station and share the definitions clearly. This review focuses on nine anatomical zones around the stomach and summarizes the history of lymph node stations in the Japanese Classification of Gastric Carcinoma. Lymph node stations will continue to be modified in the future, and the historical background may be useful in future revisions.