Cellular Differentiation and Histogenesis of Rat Glandular Stomach Cancers

The gastric and intestinal phenotypic expressions of tumor cells in 18 adenomatous hyperplasias, 33 well‐differentiated adenocarcinomas, and 16 undifferentiated adenocarcinomas (4 poorly differentiated adenocarcinomas, 10 signet‐ring cell carcinomas and 2 mucinous adenocarcinomas) induced by N‐methyl‐N’‐nitro‐N‐nitrosoguanidine or 4‐nitroquinoline‐I‐oxide in the rat glandular stomach were studied by histochemical stainings for mucin and immunohistochemical staining for pepsinogen isozyme 1 (Pg 1). By histochemical staining for mucin [by the paradoxical concanavalin A method, the modified method with labeled peanut lectin, the galactose oxidase‐Schiff (GOS) reaction, and the sialidase‐GOS reaction] and immunohistochemical staining of Pg 1, gastric cancer cells of each histological group could be clearly classified into a gastric type, including mucous neck cell pyloric gland cell, and surface mucous cell subtypes, and an intestinal type, including goblet‐cell, and intestinal absorptive cell subtypes. All tumors examined in this work consisted mainly of gastric‐type cells but intestinal‐type tumor cells were occasionally found among the gastric‐type tumor cells. The incidences of intestinal‐type cells in adenomatous hyperplasias (11.1%) and small well‐differentiated adenocarcinomas (28.6%) were significantly less (P<0.05) than that in large well‐differentiated adenocarcinomas (68.4%). The incidence of intestinal‐type cells in small undifferentiated adenocarcinomas (25.0%) was also less than that in large ones (58.3%). The present results suggest the occurrence of change of phenotypic expression of tumor cells from the gastric type to the intestinal type during growth of tumors.