Trophoblast implantation and placentation allow the survival of the young embryo and its normal development inside the uterus. In order for these processes to function properly, the trophoblast has to undergo a series of characteristic changes that lead to its adhesion and invasion of the uterus. This is achieved, among other mechanisms, by inactivation of specific tumor suppressor genes, commonly by methylation of their promoters. Cell adhesion and tissue invasion are also characteristics of malignant tumors and patterns of methylation similar to that seen in trophoblast are found in various tumor types. Another important mechanism that aids trophoblast cells invasion is their transition from epithelial to mesenchymal phenotype. Such a transition is also a common characteristic of invading malignant cells. Thus, studying tissue invasion and its control mechanisms can benefit the understanding of both the trophoblast and malignant cells behavior.