Prostate-Specific Antigen (PSA) is a glycoprotein produced by the vesicles in the cytoplasm of normal or pre-cancerous epithelial cells of the prostate. It is the most specific and sensitive tumor marker for prostate cancer. Therefore, in patients with prostate cancer, we generally conduct blood tests for PSA, especially in screening for prostate cancer, assessing the effectiveness of treatments, and for the prognosis of prostate patients, among other aspects. Additionally, other examinations are combined, such as digital rectal exams, which can also serve as a screening method for prostate cancer. Moreover, CT or MRI scans of the prostate and pelvis, as well as ultrasound examinations of the prostate, can be used in conjunction with the tumor marker PSA for a comprehensive evaluation.