The use of PSA testing remains controversial as it lacks both sensitivity and specificity for the detection of prostate cancer.1, 2 Despite the high incidence, many men diagnosed with prostate cancer will not die from the disease so it is accepted that a distinction should be made between prostate cancer that is unlikely to cause harm (‘clinically insignificant’ disease) and cancer which, if untreated, may negatively impact quality of life or lead to death (‘clinically significant’ disease). The gene discussed is KLK3; the disease is prostate cancer.