The second English edition of the Japanese Classification of Gastric Carcinoma. A Western commentary

tion, the subclassification of T1 and T2 was introduced as proposed by the UICC TNM Supplement 1993 [4], i.e., T1a 5 T1M (mucosa, muscularis mucosae), T1b 5 T1SM (submucosa), T2a 5 T2MP (muscularis propria), and T2b 5 T2SS (subserosa). According to the new Japanese edition, in patients treated by mucosal resection, submucosal carcinomas should be further subdivided into SM 1 (submucosal invasion less than 0.5 mm) and SM 2 (submucosal invasion 0.5mm or more), predominantly because longterm outcome data after endoscopic mucosal resections are not yet available. Regional lymph nodes (N). Now, as before, there are considerable differences in the classification of regional lymph nodes. First of all, in the Japanese classification the definition of regional lymph nodes is different according to the tumor localization, while in the UICC system no respective differentiation is provided. Secondly, some lymph node stations considered as regional at least for some tumor localizations by the Japanese rules (13, retropancreatic; 14v, superior mesenteric vein; 16a2 and 16b1, paraaortic middle) are always classified as distant by the UICC. In consequence, there are patients with lymph node metastases who are assigned to M0 in the Japanese system and to M1 in the UICC system. Furthermore, the subclassification of node-positive patients into N1, N2, and N3 follows different principles: in the UICC system, it is based on the number, and in the Japanese system, on the localization of the involved nodes. A translation of the UICC N classification into the Japanese system is not possible because documentation of the site of involved regional lymph nodes is not provided. On the other hand, translation of the Japanese system into the UICC N classification is possible, if for the individual lymph node stations, the number of involved nodes is documented as required in the Japanese rules. Letter to the editor