Expression of differentiation antigens in mammary and extramammary Paget's disease.

Seven cases of mammary and twelve cases of extramammary Paget's disease were studied for the presence of carcinoembryonic antigen (CEA) and apocrine epithelial antigen (AEA) using the immunoperoxidase technique. CEA was found in the Paget cells in five out of seven mammary and in all twelve cases of extramammary Paget's disease, whereas the AEA reaction was positive in six mammary and all extramammary cases. The same antigens were also found in the cells of intraductal or ductal adenocarcinomas of the breast associated with mammary Paget's disease, suggesting a common origin for the cells. In the cases of extramammary Paget's disease studied no underlying malignant neoplasms could be detected. Our findings support the suggestion that Paget cells originate in sweat gland ducts and undergo an apocrine differentiation.