ENO2 and lung cancer: Our group has previously published an analysis of six serum biomarkers: NSE, cytokeratin 19 fragment 21–1 (CYFRA 21–1), pro-gastrin-releasing peptide (Pro-GRP), squamous cell carcinoma antigen (SCC-Ag), tissue inhibitor of metalloproteinase-1 (TIMP1), and human epididymis protein 4 (HE4), and examined their ability to enhance non-invasive diagnosis and differentiation of histologic subtypes of lung cancers [13].