"Initial distortion" indicates the primary stage of tissular distortion, and which can be seen in the primary stage of a pre-tumorigenic tissue. Two-stage carcinogenesis points out that carcinogenesis occurs through two steps: initiation and promotion. Of these two steps, initiation can theoretically be considered a step: a tissue causes tissular distortion. This tissular distortion means initial distortion. That is, initial distortion indicates tissular distortion firstly occurring in a pre-tumorigenic tissue, and plays a role in the basis of the tissular distortion causing tumorigenesis.

Interestingly enough, a tissue causes initial distortion due to the structure. Organs in a human body can roughly be classified into two types: hollow and solid organs. Of these two types of organs, all the hollow organs, for instance, cause the same type of initial distortion. Specifically, a hollow organ is created as a duct, the wall of which consists of several layers. In the layers, a hollow organ frequently causes initial distortion. Thus, a hollow organ tends to cause initial distortion just like the initial distortion other hollow organs cause. I call this type of initial distortion "Layer Distortion," because its fundamental cause originates in the layers in a hollow organ.

(b) Initial Distortion Seen in The Esophagus
The esophagus, for instance, tends to easily cause initial distortion due to the relative difference in metabolic activity among layers in the wall. The esophagus is created as a duct, the wall of which consists of several layers. Of the layers, the mucosal epithelium directly touches foods and stimulants such as liquor, and easily loses the normal metabolic activity. Different from the mucosal epithelium, other layers do not directly touch foods, and do not easily lose their normal metabolic activity. By this mechanism, the esophagus causes the relative difference in metabolic activity among the layers, and which works as "Initial Distortion."