Common tumor markers for lung cancer screening If lung cancer is suspected, serum levels of tumor markers CEA, SCC, Cyfra21-1, TPA, CA125, CA242, and NSE may be elevated (positive). Carcinoembryonic antigen (CEA), originally found in adult colon cancer tissues, is a soluble glycoprotein with a complex structure. serum levels of CEA can appear significantly elevated in patients with various malignancies. However, it has a low sensitivity and a low positive rate. Therefore, CEA is a broad-spectrum tumor marker, and although it cannot be used as a specific indicator for the diagnosis of lung cancer, it still has important clinical value in the differential diagnosis of lung cancer. Squamous cell carcinoma antigen (SCC) is a glycoprotein. It was first isolated from squamous cell carcinoma tissue of the uterine cervix, and is a tumor marker with good specificity for squamous carcinoma. However, its sensitivity is low, and it can be used as an auxiliary diagnostic indicator for lung cancer. Cytokeratin 19 fragment (Cyfra21-1) is an acidic polypeptide that is mainly distributed in the alveolar epithelium. When these cells become cancerous, Cyfra21-1 can be released into the blood circulation, resulting in elevated serum levels of Cyfra21-1. Cyfra21-1 is currently the tumor marker of choice for squamous epithelial cell carcinoma, with a sensitivity of up to 60% and specificity of up to 95%. It is important for the early diagnosis, efficacy monitoring and prognosis of non-small cell lung cancer (NSCLC). Tissue polypeptide antigen (TPA) is a non-specific tumor marker, which was found in malignant tumor tissues as early as 1957, and is also a broad-spectrum tumor marker. Glycopeptide chain antigen 125 (CA125) is a very important ovarian cancer-associated antigen and is the tumor marker of choice for the diagnosis of ovarian cancer. In addition, CA125 is also present in benign and malignant exudate of lung cancer, so some patients with lung cancer also have varying degrees of elevated serum CA125. Glycoconjugate antigen 242 (CA242) is mainly used as an adjunctive diagnosis for gastrointestinal malignancies, but it also has a positive detection rate for lung cancer. Neuron-specific enolase (NSE) is a tumor marker for small cell lung cancer and neuroblastoma. When tissues become cancerous, intracellular NSE is released into the blood, resulting in increased levels of this enzyme in the serum, which is generally used in the differential diagnosis of small cell lung cancer and non-small cell lung cancer.