To investigate whether a causal role exists between ECM remodelling, myoepithelial integrin signalling and DCIS progression, we first assessed the duct-by-duct expression of myoepithelial cell integrin β6 and periductal fibronectin in serial sections of DCIS tissues without (pure DCIS) and with (DCIS/IDC) invasive disease, as well as adjacent normal breast tissue (Fig. 1c, Supplementary Table 1). Here, FN1 is linked to ductal breast carcinoma in situ.