[Implication of the "precancerous lesions" in carcinogenesis of the stomach--a cytodynamic aspect].

The most remarkable changes of human stomach, closely related to carcinogenesis are intestinal metaplasia. In order to define an interrelation between these mucosal changes and carcinogenesis, it seems to be necessary to study structural dynamics of normal and intestinalized gastric mucosa. We examined cell kinetics and morphological characteristics of human gastric mucosa, using 3H-thymidine autoradiography and scanning electron microscopic fractography. It is shown that in normal and fully developed intestinal metaplasia epithelial cells are regularly renewed within 15-60 days. A potential cancer cell, if it may appear in the otherwise normal mucosa, will be lost within this very short period of time. An experiment using hamsters confirmed this expectation. However, the situation is completely different when the gastric mucosa is in the process of intestinalization. Drastic rebuilding (Umbau) is taking place in dynamic structure of gastric gland. SEM fractography revealed this change in three-dimensional pictures. It is concluded that progression of the intestinalization keeps producing a large number of glandular fragments that are embedded in the depth of mucosa making the flow of the cellular turnover stagnant. It is inferred that the stagnation captures a potential cancer cell to make its propagation possible. Therefore, intestinalization can help the cancer cells to propagate in the body of the host. This role of the intestinal metaplasia explains many aspects of their "precancerous" characteristics.