This review article presents the improvements made in the field of molecular biology in oncology and their diagnostic and therapeutic consequences. As an illustration, three types of tumors for which these projections strongly modified the management will be used as a basis in this article: breast cancer, kidney cancer and colorectal cancer. Indeed, the last years, new prognostic factors (natural evolution of a specific patient's tumor) and predictive factors (prediction of the responsiveness to anticancer therapies) have emerged for these tumors. In addition, a better comprehension of the mechanisms implied in the development of cancers allowed the advent of many molecular-targeted therapies, which constitute a true revolution in oncology.