CA12 and ductal breast carcinoma in situ: CAXII basolateral polarity was observable in columnar cell lesions, in which bilayer integrity is preserved (Figure 5B) but was lost in intra-ductal proliferating cells in ductal carcinoma in situ (DCIS) (Figure 5C) and in cells migrating into the stromal compartment in invasive ductal carcinoma (IDC) (Figure 5D).