As a result of the application of different definitions for subtypes, in particular the basal/TN category, it is difficult to make direct comparisons between studies; however, Tamimi et al (2008) and Livasy et al (2007) use the same definition for basal, and report frequencies in DCIS of 7.7 and 8%, in contrast to the very low frequency (∼1.8%) reported on the basis of CK5/6 staining by Meijnen et al (2008). Here, KRT5 is linked to ductal breast carcinoma in situ.