KLK3 and cancer: The most commonly used classifications are the clinical TNM (tumour, node and metastases) staging (based on the presence of cancer in the prostate, degree of invasiveness in surrounding tissues, involvement of lymph nodes and the presence of distant metastases)2 and the histopathological Gleason score (based mainly on the degree of differentiation upon microscopical examination).3 The most commonly used serum biomarker for cancer progression is the prostate-specific antigen (PSA).