GRP and small cell lung carcinoma: A study comparing 102 cases of small cell lung cancer and 60 cases of benign lung tumors found that M2-pyruvate kinase, NSE, and ProGRP had sensitivities of 82.35%, 60.78%, and 77.45%, respectively, and specificities of 91.11%, 81.11%, and 86.67%, respectively, for small cell lung cancer (Li et al. 2023).