Differentiation of lobular breast cancer (LBC) cells. Upper panels: Nonneoplastic epithelium surrounded by invasive LBC cells. CK5 (blue) and CK18 (green) were detected with sequential staining, as both primary antibodies are from mouse. The basal cells (CK5) therefore stained with both secondary antibodies in this case. Lower panel: Invasive cancer cells and adjacent lobular carcinoma in situ (LCIS) stained for E-cadherin (red) and CK18 (green).