Enzymes in Tumors: Benign vs. Malignant, Tumor Markers, and Diagnostic Significance

Enzymes are present in all cells, including tumors. Their presence alone does not indicate malignancy.

Enzymes as Tumor Markers

Certain tumors overexpress or secrete specific enzymes that serve as biomarkers:

• PSA (Prostate-Specific Antigen): Serine protease; elevated in prostate cancer, BPH, prostatitis.
• Alkaline Phosphatase (ALP): Bone isoform ↑ in osteosarcoma, metastases; liver isoform in hepatobiliary disease.
• LDH (Lactate Dehydrogenase): Nonspecific; ↑ in many cancers (lymphoma, germ cell tumors), hemolysis, tissue injury.
• NSE (Neuron-Specific Enolase): Neuroendocrine tumors (small cell lung cancer, neuroblastoma).
• Prostatic Acid Phosphatase (PAP): Historical prostate cancer marker, largely replaced by PSA.

Diagnostic Use

• Screening: PSA (controversial), AFP for HCC in cirrhosis.
• Diagnosis/Staging: Marker levels correlate with tumor burden.
• Monitoring: Post-treatment decline indicates response; rise signals recurrence.

Limitations

No enzyme is perfectly specific. False positives (benign conditions) and false negatives (non-secreting tumors) occur. Always interpret in clinical context with imaging and pathology.