In the last decades, a large number of important fusion mutations have been recognized [3], including the first identified “Philadelphia chromosome” BCR-ABL gene fusion in chronic myelogenous leukemia [4], the important biomarker of synovial sarcomas, SYT–SSX gene fusion [5], and the most studied fusion TMPRSS2-ERG in prostate cancer [6]. The gene discussed is TMPRSS2; the disease is prostate cancer.