Abstract
It has become increasingly apparent that the Japanese and Western systems of classifying dysplasia and carcinoma in the gastrointestinal tract are not the same. The implication of these differences is that in an article in a Western journal on gastrointestinal ‘cancer’ originating from Japan, it is often impossible to repeat the study to confirm or refute it because of these differences in definitions. ‘Carcinoma’ is diagnosed in Japan by virtue of its structural and cytological features but by invasion in the Western system. Adenoma does not mean a dysplastic lump in the Japanese system (although it can), but in most cases is similar to low grade dysplasia irrespective of the macroscopic and/or endoscopic appearances (hence flat and depressed adenomas in the Japanese system); however, most examples of high grade dysplasia in the Western system, as well as some low grade dysplasia, are ‘cancer’ in the Japanese system. Conversely, both have conceptual areas that are useful in the other’s system.