Similar to CA15-3, carbohydrate antigen 27-29 (CA27-29) is a critical epitope for the MUC1 protein.243 With a sensitivity of 84% for breast cancer detection, CA27-29 is primarily utilized in breast cancer patients for diagnosis, and efficacy evaluation.243 Additionally, it also be used in combination with other markers to increase the specificity of breast cancer diagnosis.252 The elevated CA27-29 is also observed in other cancers including CRC, stomach cancer, pancreatic cancer, ovarian cancer, and benign diseases of the breast and liver.253. This evidence concerns the gene MUC1 and breast cancer.