Pathophysiology
Clinical meaning
Tumor markers are substances produced by cancer cells or by the body in response to cancer that can be detected in blood, urine, or tissue samples. While tumor markers are valuable tools in oncology, the practical nurse must understand that most tumor markers are NOT used for cancer screening in the general population because they lack sufficient sensitivity (ability to detect all cancers) and specificity (ability to distinguish cancer from non-cancerous conditions). The primary clinical applications of tumor markers are: monitoring treatment response in diagnosed cancers, detecting recurrence after treatment, estimating prognosis, and in some specific cases, aiding in diagnosis when combined with other clinical findings. Prostate-specific antigen (PSA) is a glycoprotein produced by both normal and malignant prostate epithelial cells. While PSA is the most widely used cancer screening marker, it is important to understand that elevated PSA is NOT specific for prostate cancer. Benign prostatic hyperplasia (BPH), prostatitis, urinary tract infection, recent ejaculation, and digital rectal examination can all elevate PSA levels, leading to false-positive results. The normal range is generally considered below 4.0 ng/mL, though age-specific reference...