Mucin histochemical analysis of minute gastric differentiated adenocarcinoma.

Fifty-six surgically resected intramucosal differentiated adenocarcinomas (DA) of the stomach with a maximum diameter of less than 5 mm were analyzed by mucin histochemistry. Gastric type phenotypic expression was observed in 41.1% of cases, intestinal type in 28.6% and gastric-intestinal type in 28.6% of all cancers. Gastric type phenotypic expression was the most frequent. As the tumor diameter increased, the incidence of DA with gastric phenotype tended to decrease. Intestinal metaplasia of the cancer's surrounding mucosa was absent or slight in DA with gastric phenotype, but moderate to severe in DA with gastric-intestinal phenotype and intestinal phenotype. Morphologically and mucin histochemically, intestinal metaplasia surrounding DA with gastric phenotype was immature and incomplete compared with DA with gastric-intestinal phenotype or intestinal phenotype. It is suggested that a large amount of DA with gastric phenotype is histogenetically derived from the gastric gland proper without intestinal metaplasia. However, as the tumor grows and intestinal metaplasia progresses, intestinal type phenotypic expression appears and then DA with gastric phenotype changes into DA with gastric-intestinal phenotype or intestinal phenotype.