Using immunohistochemistry, quantitative PCR, and western blot analysis, we detected significant PADI4 expression in tumour cells of various malignancies, including breast carcinomas, lung adenocarcinomas, hepatocellular carcinomas, oesophageal squamous cancers, colorectal adenocarcinomas, renal cancers, ovarian adenocarcinomas, endometrial carcinomas, uterine adenocarcinomas, bladder carcinomas, and chondromas, as well as in other metastatic carcinomas. Here, PADI4 is linked to lung adenocarcinoma.