FN1 and ductal breast carcinoma in situ: Immunohistochemical staining for periductal fibronectin revealed that the adjacent normal breast ducts had little expression (6%), whereas the percent of positive DCIS ducts was higher in DCIS/IDC (87%) compared with pure DCIS (68%), with no difference between non-high and high-grade pure DCIS (Fig. 1g, i and Supplementary Table 3).