One of the most intriguing questions related to cancer is why approximately two out of three people never develop cancer? It has been proposed that this variability in cancer resistance may be due to differences in the efficiency of certain protective mechanisms, which are known to inhibit the growth of neoplastic cells. Here we focus on the mechanism known as microenvironmental control. There is a large amount of evidence that a majority of disseminated tumor cells present in the human body never develop into clinical tumors, and that the direct physical contact between normal and tumoral cells appears to be a necessary condition for such resistance to cancer. By using a system of ordinary differential equations, we model contact-controlled tumor growth and are able to simulate the three expected modes of growth: expansive, contractive and stable, thus mathematically supporting the feasibility of microenvironmental control.