CYFRA 21-1 Unit Converter

CYFRA 21-1 is a soluble fragment of cytokeratin 19 (CK19), a structural protein found in the cytoskeleton of epithelial cells. When epithelial cells are damaged, undergo rapid turnover, or die, fragments of CK19 are released into the bloodstream, where they can be measured.

CYFRA 21-1 is primarily used as a tumor marker for non-small cell lung cancer (NSCLC), especially the squamous cell carcinoma subtype. It is not a screening test for cancer. Instead, it is most valuable for monitoring disease progression and treatment response in patients with a confirmed diagnosis.

Elevated levels can also occur in other epithelial cancers and in several benign conditions, so results must always be interpreted alongside imaging, biopsy findings, and other clinical evidence.

Cytokeratin 19 is a structural protein found in the cytoskeleton of epithelial cells, with highest expression in simple and pseudostratified epithelia lining the airways (bronchi), gastrointestinal tract, urinary tract, and various glandular ducts. Fragments are released into the bloodstream when these cells undergo apoptosis, necrosis, or abnormal proliferation.