KLK3 and neoplasm: Further investigations revealed negative tumor markers (namely, carcinoembryonic antigen (CEA), prostate-specific antigen (PSA), alpha-fetoprotein (AFP), carbohydrate antigen 19-9 (CA 19-9), cancer antigen 125 (CA 125), and cancer antigen 15-3 (CA 15-3)) and negative biochemical markers for multiple myeloma (Table 1).