From January 2017 to December 2018, 86 patients with invasive ductal carcinoma of the breast with nipple discharge (breast cancer group) and 50 patients with ordinary breast duct hyperplasia with nipple discharge (benign control group) were selected, and the levels of CA125, CA153 and CEA in nipple discharge and serum were detected by electrochemiluminescence immunoassay. Here, CEACAM5 is linked to breast cancer.