AFP and lung adenocarcinoma: AFP is a glycoprotein originally identified as the first oncoprotein and is now widely used as a biomarker in hepatocellular carcinoma screening (45, 46), Elevated serum AFP levels have also been reported in some patients with primary lung cancer (47, 48), and extremely high concentrations are a distinguishing feature of hepatoid adenocarcinoma of the lung (49), However, the intrinsic relationship between AFP and lung adenocarcinoma remains poorly understood and warrants further investigation.