[Immunohistochemical studies of breast and extra-mammary Paget's disease indicate an apocrine differentiation].

Using the PAP technique, paraffin-embedded and formalin-fixed tissue sections taken from 11 patients suffering from Paget's disease (5 mammary, 6 extramammary cases) were stained with antibodies against keratin, actin, S 100 protein, CEA, HMFG 1, cytokeratin 6 and 18 (Dako-CK-1), as well as the lectin SBA. We did not find any differences between mammary and extramammary Paget's disease. In both forms of the disease, all tumor cells showed reaction to antibodies against HMFG 1 and CEA and, in 50 to 100%, to the lectin SBA. The other antibodies investigated did not react with Paget's cells. Since HMFG 1 and Dako-CK-1 are selective markers of apocrine and eccrine sweat gland structures, respectively, our results suggest apocrine differentiation of both mammary and extramammary Paget's disease. At the same time, our findings rule out a possible histogenesis of Paget's cells from melanocytes (positive for S 100 protein) or keratinocytes (positive for Dako-CK-1 and antikeratin).