Relationship between biological behavior and phenotypic expression in undifferentiated-type gastric carcinomas

Background. It has been proved that some differentiated-type gastric carcinomas have a gastric phenotype. Similarly, it can be conjectured that some undifferentiated-type gastric carcinomas have an intestinal phenotype and that there are biological differences between undifferentiated-type gastric carcinomas with a gastric phenotype and those with an intestinal phenotype. We classified the phenotypes of early undifferentiated-type gastric carcinomas and investigated the relationship between their biological behavior and the phenotypes. Methods. Sixty lesions of intramucosal undifferentiated-type gastric carcinoma were classified into four phenotypes; gastric type, incomplete-intestinal type, complete-intestinal type, and unclassified type, according to the expression of CD10, MUC2, small-intestinal mucinous antigen (SIMA), human gastric mucin (HGM), or concanavalin A (ConA). Results. The incidence of gastric-type carcinoma, incomplete-intestinal-type carcinoma, and complete-intestinal-type carcinoma was 33% (20 cases), 65% (39 cases), and 2% (1 case), respectively. There was no significant difference in any of the clinicopathological factors examined between the 20 gastric-type carcinomas and the 40 intestinal-type carcinomas, but there were significant differences in the morphological findings. Intestinal-type carcinomas had a glandular structure more frequently than the gastric-type carcinomas. The spreading pattern of gastric-type carcinomas showed a middle-layer type more frequently than the intestinal-type carcinomas. Conclusion. Undifferentiated-type gastric carcinomas frequently expressed an intestinal phenotype. There were differences in the growth patterns between undifferentiated-type gastric carcinomas with a gastric phenotype and those with the intestinal phenotype.