Background: There have been many studies on gastric carcinoma in populations with contrasting cancer risks. We aimed to find out whether the criteria for the histological diagnosis of early gastric carcinoma were comparable in Western countries and Japan.
Methods: Eight pathologists from Japan, North America, and Europe individually reviewed 35 microscope slides: 17 gastric biopsy samples and 18 endoscopic mucosal resections taken from 17 Japanese patients with lesions ranging from early gastric cancer to adenoma, dysplasia, and reactive atypia. The pathologists were given a list of pathological criteria and a form on which they were asked to indicate the criteria on which they based each diagnosis.
Findings: For seven slides most Western pathologists diagnosed low-grade adenoma/dysplasia, whereas the Japanese diagnosed definite carcinoma in four slides, suspected carcinoma in one, and adenoma in only two. Of 12 slides with high-grade adenoma/dysplasia according to most Western pathologists the Japanese gave the diagnosis of definite carcinoma in 11 and suspected in one. Of six slides showing high-grade adenoma/dysplasia with suspected carcinoma according to most Western pathologists the Japanese diagnosed definite carcinoma in all. There were no major differences in the diagnoses of three slides showing reactive epithelium and seven slides with clearly invasive carcinoma. When the opinion of the majority of the pathologists was taken as the final diagnosis there was agreement between Western and japanese in 11 of the 35 slides (kappa coefficient 0.15 [95% CI 0.01-0.29]). Presence of invasion was the most important diagnostic criterion for most Western pathologists whereas for the Japanese nuclear features and glandular structures were more important.
Interpretation: In Japan, gastric carcinoma is diagnosed on nuclear and structural criteria even when invasion is absent according to the Western viewpoint. This diagnostic practice results in almost no discrepancy between the diagnosis of a superficial biopsy sample and that of the final resection specimen. This may also contribute to the relatively high incidence and good prognosis of gastric carcinoma in Japan when compared with Western countries.