A 60-year-old heavy smoker presents with chronic cough and a central cavitating lung mass. Biopsy shows large polygonal cells with intercellular bridges and keratin pearl formation. The most appropriate tumour marker to measure in serum is:
- A CYFRA 21-1 (cytokeratin fragment) ✓
- B CEA (carcinoembryonic antigen)
- C NSE (neuron-specific enolase)
- D ProGRP (pro-gastrin-releasing peptide)
Correct answer: A. CYFRA 21-1 (cytokeratin fragment)
Explanation
The biopsy describes squamous cell carcinoma of the lung (intercellular bridges, keratin pearls). CYFRA 21-1, a soluble fragment of cytokeratin 19, is the most sensitive and specific serum marker for squamous cell lung carcinoma and is used to monitor treatment response and recurrence. NSE and ProGRP are markers for small cell lung carcinoma (neuroendocrine). CEA is associated with adenocarcinoma and other carcinomas but has lower specificity for squamous cell lung cancer than CYFRA 21-1.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.