CYFRA 21-1

**Semantic type:** Amino Acid, Peptide, or Protein

**Definition:** Fragments of keratin, type I cytoskeletal 19 (KRT19; cytokeratin 19) that are not sequestered in insoluble intermediate filament protein complexes. These KRT19 fragments are used as tumor markers and as prognostic markers for several neoplastic diseases.

**Synonyms:** - Cytokeratin 19 Fragment - Cytokeratin-19 Fragments 21-1