ENO2 and non-small cell lung carcinoma: Presently, only a few circulating protein-based biomarkers with relatively low specificities (e.g., cytokeratin 19 fragment (CYFRA 21-1, specificity 76%), carcinoma embryonic antigen (CEA, specificity 52%), carbohydrate antigen 125 (CA125, specificity 52%), carbohydrate antigen 153 (CA153), carbohydrate antigen 199 (CA199) and neuron-specific enolase (NSE, specificity 22%)) have been incorporated into clinical practice for NSCLC [51,52,53,54,55,56].