CA125 is a common tumor biomarker, which is present in normal tissues, such as peritoneal/pleural mesothelial tissue cell surface, reproductive organ epithelium, etc.[16] CA125 can be increased in patients with gynecological tumors, lung cancer and other malignant tumors, and it is related to clinical stage and prognosis.[17–19] When the serous cavity is stimulated by inflammation or malignant transformation, CA125 can be elevated in serous cavity effusion. Here, MUC16 is linked to lung cancer.