Besides some extensively characterized human fusogens such as syncytin-1 and -2 [52,53,54,55,56], myomerger, myomaker, actin remodeling proteins [68,70,71,117,118,119,120] as well as Izumo1 and Juno [72,73,74,75], viral fusogens or human endogenous retroviruses (HERVs) also display properties for fusion and synyctia formation capacity associated with a possible role in carcinogenesis and tumor progression. This evidence concerns the gene ERVW-1 and neoplasm.