Gastric or intestinal phenotypic expression in the carcinomas and background mucosa of multiple early gastric carcinomas

Aims: The differences in phenotypic expression between multiple early gastric carcinomas (EGCs) and solitary EGCs were evaluated in this study. Methods and results: Fifty-three cases (53 lesions) of solitary EGCs and 50 cases (112 lesions) of multiple EGCs were studied. According to the classification of intestinal metaplasia, the phenotypes of carcinomas and background mucosa were classified into four categories - complete intestinal type, incomplete intestinal type, gastric type and unclassified type - based on the combination of expression of CD10 (small intestinal brush border), MUC2 (intestinal goblet cell), HGM (gastric foveolar epithelium) and Con A (gastric pyloric glands). The incidence of gastric-type carcinomas (48%) and the incidence of incomplete intestinal-type background mucosa (75%) among the multiple EGCs was higher than among the solitary EGCs. There was a significant difference in distribution of phenotypic expression of carcinomas and background mucosa between the solitary EGCs and the multiple EGCs, the latter being associated with incomplete intestinal metaplasia. Conclusions: Both the carcinomas and the background mucosa of multiple EGCs have an unstable status, since they more commonly possess the hybrid phenotype of the stomach and the small intestine than does solitary EGC. Such instability is considered to contribute to a high neoplastic potential and the multiple occurrence of carcinomas.