Human endogenous retrovirus (HERVs) integrated in the human genome millions of years ago and became astable part of the inherited genetic material. Most of these HERVs are dysfunctional due to numerous mutations andthus making it impossible to generate a full, infectious retrovirus particle from a single genetic locus. However, manyHERVs are still exceptionally well preserved and maintain Open Reading Frames encoding functional viral proteins.The permanence of HERV ́s genes along evolution suggests that these elements have proven beneficial to humansurvival. In this regard, the expression of certain HERV proteins is implicated in important physiological functions,such as placental development. Nevertheless, reactivation of HERVs has frequently been observed in a variety ofhuman tumors suggesting their potential to contribute to malignant progression. Considering the role of HERVs inthe carcinogenesis process, the purpose of this mini review is to deepen into HERVs expression and its possibleimplication in hemato-oncologic disease development.