[Natural history of human cancer]

Two important subjects in natural history of human cancer were reviewed and discussed. It is noted high incidence of latent cancer or microcancer in the thyroid, prostate and stomach. From these results we postulate that cancerization and manifestation of microcancer is different steps in cancer development and manifestors play an important role for clinical manifestation of microcancer. We proposed the concept of the basic cancer and the variable cancer. The basic cancer is a proper cancer of a certain organ and stable in its incidence, while the variable cancer is a cancer whose incidence varies by environmental conditions.