DIFFERENCES IN THE DIAGNOSTIC-CRITERIA USED BY JAPANESE AND WESTERN PATHOLOGISTS TO DIAGNOSE COLORECTAL-CARCINOMA

BACKGROUND. In view of the many studies of early stage colorectal carc inoma from Japan, it is essential to know whether the criteria for the histologic diagnosis of colorectal carcinoma are similar in Japan and Western countries. METHODS. Eight expert pathologists from Japan (4), North America (2), and Europe (2) individually reviewed microscope sl ides of 20 colorectal lesions from Japanese patients who had undergone endoscopic mucosal resection or surgery because early stage carcinoma and/or adenoma was suspected. The pathologists indicated the patholog ic findings on which they based each diagnosis. RESULTS. For 11 slides that showed adenoma according to the Western pathologists with low gr ade dysplasia according to at least half of them, the Japanese diagnos ed definite carcinoma with or without adenoma in 4 cases and adenoma i n 5, and in 2 cases they were equally divided between a diagnosis of a denoma and carcinoma. For five slides showing adenoma with high grade dysplasia according to the West ern pathologists, the Japanese diagnos ed definite carcinoma with adenoma in three cases and adenoma in one, and in one case they were equally divided between a diagnosis of adeno ma and carcinoma. For one case in which the Western pathologists were equally divided between a diagnosis of carcinoma and adenoma with high grade dysplasia, all the Japanese pathologists diagnosed definite car cinoma with or without adenoma. Three slides showed definite carcinoma with or without adenoma, according to both the Western and the Japane se pathologists. The presence of invasion was the most important diagn ostic criterion of colorectal carcinoma for the Western pathologists, whereas for the Japanese the nuclear features and glandular structures were more important. CONCLUSIONS. In Japan, colorectal carcinoma is d iagnosed on the basis of nuclear and structural criteria, even in case s considered by Western pathologists to be noninvasive lesions with lo w grade dysplasia. This diagnostic practice may contribute to the rela tively high incidence of early stage colorectal carcinoma reported in Japan as compared with Western countries. (C) 1998 American Cancer Soc iety.