MKI67 and ductal breast carcinoma in situ: Recently, there has been a large number of studies on the Ki-67 marker index and its role in cancer, and it has been found that the expression level of Ki-67 increases successively from benign breast tumors, to ductal carcinoma in situ, and then to invasive breast cancer, and this is believed to be related to the occurrence, development, recurrence, and metastasis of some tumors.