MMP11 and ductal breast carcinoma in situ: As a key element in tumour invasion and metastasis, a high level of MMP11 was previously proven to correlate with poor prognosis in invasive breast cancer patients.22,23 According to our study, the decrease in MMP11 expression in IDC/DCIS tumours may play an important role in having a relatively low RS, which might also lead to better tumour biological behaviour.