KLK3 and malignant colon neoplasm: Eighteen (53%) of these 34 were referred after documentation of significantly elevated PSA levels (>50 ng/mL), 15 (44.1%) were referred because of prominent clinical symptoms (11 had urinary symptoms, 4 had bone pain), and 1 (2.8%) was referred because of focal prostatic 18F-FDG uptake observed on 18F-FDG PET/CT performed for colon cancer follow-up.