CYFRA 21-1 is a blood tumor marker that measures a soluble fragment of cytokeratin-19, primarily used to monitor non-small cell lung cancer (NSCLC).
CYFRA 21-1 is a tumor marker: a fragment of cytokeratin 19, a protein found in epithelial cells.
It’s released into the blood when those cells break down, so levels rise in some cancers.
Primary Use: Tracking treatment response, disease progression, and detecting relapses in diagnosed NSCLC (especially squamous cell carcinoma).
Not for Screening: It is not recommended for general cancer screening or early diagnosis because benign conditions can also raise levels.
Reference Cutoff: Normal or standard baseline thresholds typically hover around 3.3 ng/mL, though values depend on the specific assay platform used by the laboratory.
False Positives / Confounders: Levels can be elevated due to benign lung diseases (such as pneumonia or tuberculosis), sepsis, renal (kidney) dysfunction, or bladder/gynaecological conditions.
Most useful in non-small cell lung cancer, especially squamous cell type Also elevated in bladder, head and neck, cervical, and esophageal cancers
Not specific or sensitive enough for screening Can be mildly raised by non-cancer causes: kidney failure, liver disease, and benign lung conditions like pneumonia, TB, or COPD
A single value means little on its own.