Tumor markers, also known as tumor markers, are a class of substances that characteristically exist in malignant tumor cells, or are abnormally produced by malignant tumor cells, or are produced by the host in response to the stimulation of the tumor, and can reflect the occurrence and development of tumors, and monitor the response of the tumors to the treatment. Tumor marker detection: among common tumors, lung cancer has the most markers, including proteins, endocrine substances, enzymes, peptides and various antigenic substances. Carcinoembryonic antigen (CEA) is elevated in all types of lung cancer, but most obviously in adenocarcinoma. Soluble membrane antigens CA-50, CA-125 and CA-199 have certain value in the diagnosis of squamous carcinoma, and neuronal enolase (NSE) is mainly used in the diagnosis of small cell lung cancer. Others, such as antitrypsin (AAT), placental alkaline phosphatase (PAKP), amylase, aromatic hydrocarbon hydroxylase (AHH), phosphohexose isomerase (PHI), and isoenzymes of lactate dehydrogenase (LDH-5, LDH-3), and glutathione S-transferase, have certain value. Generally tumor markers are elevated more than 2-fold to be of diagnostic value. For the time being, tissue cytology is still the gold standard for lung cancer diagnosis, and tumor marker testing can only be used as an indicator for observing changes in the condition.