The detection results of carcinoembryonic antigen (CEA), alpha fetoprotein (AFP), carbohydrate antigen 125 (CA125), carbohydrate antigen 199 (CA199) and carbohydrate antigen 153 (CA153) in patients with breast cancer were significantly higher than those in patients with benign breast tumours. The gene discussed is CEACAM5; the disease is breast cancer.