Diagnostic criteria for gastrointestinal carcinomas in Japan and Western countries: proposal for a new classification system of gastrointestinal epithelial neoplasia.

BACKGROUND: Large differences have been found between Western and Japanese pathologists in their diagnosis of adenoma/dysplasia and early carcinoma for gastric, colorectal and oesophageal epithelial neoplastic lesions. Common worldwide terminology based on clinical usefulness, that is, on neoplastic severity and depth of invasion, is needed.
METHODS: Thirty-one pathologists from 12 countries reviewed 35 gastric, 20 colorectal and 21 oesophageal biopsy and resection specimens. The extent of diagnostic agreement between those with Western and Japanese viewpoints was assessed by kappa statistics.
RESULTS: Suspected or definite carcinoma was diagnosed in 17-66% 'of gastric, in 5-40% of colorectal, and in 10-67% of oesophageal slides by pathologists with a Western viewpoint, but in 77-94% of gastric, in 45-75% of colorectal and in 81-100% of oesophageal slides by pathologists with a Japanese viewpoint (from Japan, Germany, Austria and UK). Overall, there was poor agreement between the conventional Western and Japanese diagnoses (kappa values lower than 0.3 for gastric, colorectal and oesophageal lesions). There was much better agreement among the pathologists (kappa values higher than 0.5 for gastric and colorectal lesions) when the original assessments of the slides were regrouped into the five categories of the following classification of GI epithelial neoplasia we hereby propose: C1, negative for neoplasia; C2, indefinite for neoplasia; C3, mucosal low-grade neoplasia (low-grade adenoma/dysplasia); C4, mucosal high-grade neoplasia (high-grade adenoma/dysplasia plus mucosal carcinoma); C5, submucosal invasion of neoplasia.
CONCLUSIONS: The intercountry differences in the diagnoses of adenoma/dysplasia and early carcinoma can, in large part, be resolved by adopting terminology based on neoplastic severity and depth of invasion. Problems with defining intramucosal invasion are thus avoided. Moreover, grouping high-grade adenoma/dysplasia and mucosal carcinoma together in one category is clinically useful, as patients with small mucosal neoplastic lesions can be cured by endoscopic local resection.