CEACAM5 and neoplasm: Serum tumor markers such as carcinoembryonic antigen (CEA), squamous cell carcinoma antigen (SCCA), and cytokeratin 19 fragments (CYFRA 21-1) are clinically used for NSCLC screening and recurrence evaluation, and some of these tumor markers have been shown to be correlated with prognostic factors such as higher TNM stages [4, 5].