Positive breast cancer E-CAD in pathologic immunohistochemistry indicates a low degree of malignancy, whereas negative breast cancer indicates a higher degree of malignancy. Breast cancer E-CAD, usually an important intercellular adhesion molecule, is closely linked to tumorigenesis or prognosis, among others. Since the expression of E-CAD is higher than normal in breast cancer, gastric cancer, prostate cancer, and melanoma, which is negatively correlated with the clinical grade of the tumor, it can be used as an independent survival and prognostic factor. The expression is usually downregulated or absent in cervical intraepithelial neoplasia. Currently, serum E-CAD has been used as a new diagnostic marker and indicator for efficacy assessment and prognosis prediction. It is important for the study of tumor development. If breast cancer E-CAD is abnormal, you should go to the hospital in time and take active treatment under the doctor’s guidance, so as not to delay the condition.