Regarding tumor markers in clinical oncology, all of the following statements are correct EXCEPT:

Explanation

## Tumor Markers: Specificity and Clinical Applications ### Overview of Tumor Markers Tumor markers are biochemical substances produced by cancer cells or by the body in response to cancer. They are used for screening, diagnosis, prognosis, and monitoring treatment response. ### Analysis of Each Statement | Marker | Cancer Type | Sensitivity | Specificity | Clinical Use | |--------|-------------|-------------|-------------|---------------| | AFP | HCC, NSGCT | High in HCC | Moderate (elevated in cirrhosis, hepatitis) | Diagnosis, monitoring | | PSA | Prostate cancer | Moderate | **LOW** (elevated in BPH, prostatitis) | Screening, monitoring | | CEA | Colorectal, lung | Moderate | Low (elevated in smokers, benign disease) | Monitoring recurrence | | hCG | Testicular NSGCT, choriocarcinoma | High | High | Diagnosis, monitoring | ### Key Point: PSA Specificity Myth **PSA is NOT 100% specific for prostate cancer.** This is a critical misconception in oncology. PSA is elevated in: - Benign prostatic hyperplasia (BPH) — most common cause - Prostatitis (acute and chronic) - Urinary tract infection - Recent digital rectal examination or ejaculation **High-Yield:** PSA has a sensitivity of ~80% and specificity of only ~25% for prostate cancer. It is used for monitoring known prostate cancer, not for definitive diagnosis. ### Clinical Pearl: Marker Limitations No single tumor marker is 100% specific or sensitive. All markers can be elevated in benign conditions, inflammatory states, or other malignancies. This is why: - Markers are used in conjunction with imaging and histopathology - Serial measurements (trend) are more useful than single values - Cutoff values are relative, not absolute ### High-Yield: Marker-Cancer Associations **Mnemonic: "ACHE"** - **A**FP → hepatocellular carcinoma, germ cell tumors - **C**EA → colorectal, lung cancers - **H**CG → testicular (NSGCT), choriocarcinoma - **E**strogen/Progesterone receptors → breast cancer [cite:Harrison 21e Ch 81] [cite:Robbins 10e Ch 6]