Metastasis is the sequence of interrelated steps by which primary tumor cells acquire the capability to invade adjacent tissue, enter the systemic circulation (intravasate), translocate through the vasculature, arrest in distant capillaries, extravasate into the surrounding tissue parenchyma, and, finally, proliferate from micrometastases into macroscopic secondary tumors [1, 2]. This metastatic process is the cause of 90 percent of deaths in patients with solid tumors [1, 2]. Therefore, unraveling the inner mechanisms of the pathogenesis of metastasis at systemic, cellular, and molecular levels has become a major goal of cancer research [1, 2].
In recent years, the contribution of epigenetics to the field of cancer has been of paramount importance, because cancer is both a genetic and an epigenetic disease  and because epigenetic alterations are also involved in the metastatic process . Thus, cancer cells have to gain an epigenotype to disseminate from the primary tumor mass or to survive and proliferate at a secondary tissue site .
We are still in the early stages of deciphering the timing and hierarchy of these epigenetic lesions; we need to know how epigenetic mechanisms operate in normal and cancer cells to understand the epigenetic changes that occur in metastasis. This information will allow us to identify new metastasis-related genes, to discover new epigenetic biomarkers that may help identify the diagnostic signatures of metastasis, and to develop new cancer therapies based on epigenetic drugs .