Cytokeratin 19 Fragment (CYFRA 21-1). CYFRA 21-1 is a prognostic marker in patients with non-small cell lung cancer. Among tumor marker tests for non-small cell lung cancer, CYFRA 21-1 has consistently been shown to have the highest diagnostic sensitivity (~70 percent). Description: Human breast adenocarcinoma cell line. Alternative Names: CYFRA -1 21, CYFRA-1-21 protein, CYFRA-1-21, Cytokeratin 19 Fragment protein, CYFRA -1 21 protein, CYFRA 21-1