Up to 60% of primary prostate cancer can be defined by a gene fusion between the androgen-dependent transcription factor transmembrane serine protease 2 (i.e., TMPRSS2) and an ETS family oncogene, most frequently ETS-related gene (ERG) (12, 13), which can be identified by the surrogate detection of ERG protein overexpression by immunohistochemistry (IHC) (14). The gene discussed is ERG; the disease is prostate carcinoma.