Expression of cytokeratin and erbB-2 oncoprotein in Paget's disease of the nipple. An immunohistochemical study.

The occurrence of epithelial membrane antigen (EMA), low molecular weight cytokeratin (CK) and erbB-2 oncoprotein was investigated in twenty-eight cases of Paget's disease of the nipple (PD) to determine their diagnostic usefulness. The ABC technique with monoclonal antibodies was used on formalin-fixed, paraffin-embedded tissue. The Paget's cells showed positive immunoreactivity for all three antigens investigated in a high percentage of PD. Immunoreactivity for CK and erbB-2 oncoprotein was restricted to the Paget's cells, whereas EMA in some cases also stained the adjacent keratinocytes. Since CK and/or erbB-2 oncoprotein occurred in 93% of the cases, we conclude that demonstration of both antigens is useful in the diagnosis of PD. ErbB-2 oncoprotein was also found to be expressed in a high percentage of the underlying intraductal and invasive carcinomas.