KLK3 and prostate cancer: Following surgical treatment of prostate cancer, prostate-specific antigen (PSA) can be used as an indicator for identifying residual disease or recurrence [2]; however, due to the infrequent occurrence of the urethral metastasis, the diagnosis can be easily missed or overlooked in patients with stable or low PSA, unless clinicians maintain a high index of suspicion even years after definitive prostate cancer therapy.