The group of DCIS tumours with a ki67 cell proliferation of ⩾10% (n=90) was associated with 79% COX-2 positivity compared to 55% in the group with <10% (n=93) of cell expressing the Ki67 antigen (P<0.0001, χ2 test, Table 2). Here, MKI67 is linked to ductal breast carcinoma in situ.