Analysis of mucin, p53 protein and Ki‐67 expressions in gastric differentiated‐type intramucosal neoplastic lesions obtained from endoscopic mucosal resection samples: A proposal for a new classification of intramucosal neoplastic lesions based on nuclear atypia

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Abstract
There are differing views between Western and Japanese pathologists on the use of histological criteria to classify gastrointestinal tumors. It is therefore a priority to create a new histological classification of the stomach in order to resolve the confusion. Expression patterns were examined of mucin (MUC2, CD10, MUC5AC, pyloric gland‐type mucin), p53 protein, and Ki‐67 in tumor cells according to the following new classification system for differentiated‐type intramucosal neoplastic lesions of the stomach, based on nuclear atypia: borderline neoplasia (adenoma (including dysplasia), indefinite tumor of adenoma or low‐grade cancer, and low‐grade cancer) and definite carcinoma (intermediate cancer, and high‐grade cancer). The resulting grades were: adenoma, 23; indefinite tumor for adenoma or low‐grade cancer, 6; low‐grade cancer, 28; intermediate cancer, 48; high‐grade cancer, 20. While the frequency of intestinal‐type borderline neoplasias was higher than that of definite carcinomas, the mixed‐type of definite carcinomas occurred with higher frequency than borderline neoplasias. The p53 protein overexpression and the Ki‐67‐positive rate increased with an increase in the grade assigned according to the new classification. The correlated expression levels of p53 protein, Ki‐67, and various mucins, support the conclusion that this classification of intramucosal neoplastic lesions is useful for obtaining a consensus diagnosis of gastric intramucosal neoplasia between pathologists and gastrointestinal clinicians.