Using sandwich ELISA, we detected higher levels of PADI4 and citrullinated AT levels in the plasma of patients with malignant tumours, including those with breast carcinomas, hepatocellular carcinomas, lung carcinomas, oesophageal carcinomas, gastric cancer, colon cancer, rectal cancer, pancreatic cancer, ovarian carcinomas, bladder carcinomas, uterine myomas, thyroid carcinomas, and prostate carcinomas. The gene discussed is PADI4; the disease is gastric cancer.