FST and small cell lung carcinoma: In this study, we firstly investigated the association of serum FST levels with patients in two broad histological subtypes of lung cancers: small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC), and NSCLC was subdivided into lung adenocarcinoma (LADC), squamous cell carcinoma (SCC), lung adenosquamous cell carcinoma (LASC) and large cell lung cancer (LCLC).