Hereditary prostate cancer is estimated to account for 5-10% of all prostate cancer cases, but the identification of highly penetrant genes has been difficult. HOXB13 was recently identified as a susceptibility gene for prostate cancer (PrCa) when the rare, but recurrent, germline mutation [G84E, p.(Gly84Glu)] was found in men of European descent, conferring an increased PrCa risk of 4.51-fold.