Src associated in mitosis, of 68 kDa (Sam68) is a KH domain RNA-binding protein that belongs to the signal transduction and activation of RNA family. Although ubiquitously expressed, Sam68 plays very specialized roles in different cellular environments. In most cells, Sam68 resides in the nucleus and is involved in several steps of mRNA processing, from transcription, to alternative splicing, to nuclear export. In addition, Sam68 translocates to the cytoplasm upon cell stimulation, cell cycle transitions or viral infections, where it takes part to signaling complexes and associates with the mRNA translation machinery. Recent evidence has linked Sam68 function to the onset and progression of endocrine tumors, such as prostate and breast carcinomas. Notably, all the biochemical activities reported for Sam68 seem to be implicated in carcinogenesis. Herein, we review the recent advancement in the knowledge of Sam68 function and regulation and discuss it in the frame of its participation to neoplastic transformation and tumor progression.