KLK3 and neoplasm: The actual cancer-screening tests for the four most prevalent tumor types (CRC, LC, PCa, and BC) are mainly based on radiological images (Computed Axial Tomography (CAT), mammography, and multiparametric magnetic resonance for LC, BC, and PCa respectively), some biomarkers such as PSA in PCa or fecal occult blood for CRC, and other invasive interventions such as colonoscopy for CRC [11,12,13,14].