Mammary Paget's disease and extramammary Paget's disease are rare 
intraepithelial neoplasms. Mammary Paget's disease is almost exclusively 
associated with underlying invasive breast carcinoma or high-grade ductal 
carcinoma in situ (DCIS G3). Extramammary Paget's disease arises in areas rich 
in apocrine glands and is suspected to have apocrine gland origin. The aim of 
the study was to investigate the presence of estrogen receptor (ER), 
progesterone receptor (PR), androgen receptor (AR) and Her2/neu in a large 
number of cases. We investigated 58 cases of mammary and 23 cases of 
extramammary Paget's disease. Formalin-fixed and paraffin-embedded tissues were 
analyzed using antibodies against AR, PR, ER and Her2/neu according to 
standardized procedures. In mammary Paget's disease, positive immunoreactions 
for Her2/neu, AR and ER were observed in 56 of 58 (97%), 51 of 58 (88%), and 
respectively in six of 58 (10%) cases. All cases of mammary Paget's disease were 
negative for PR and showed a coexpression of Her2/neu and AR in 51 out of 58 
cases (88%). In extramammary Paget's disease, positive immunoreactions for AR, 
Her2/neu and ER were observed in 18 of 23 (78%), 12 of 23 (52%), and 
respectively in 1 of 23 (4%) cases. All cases of extramammary Paget's disease 
were negative for PR and showed a coexpression of AR and Her2/neu in 12 out of 
23 cases (52%). In contrast to ER and PR, AR and Her2/neu are commonly expressed 
in mammary and extramammary Paget's disease. The knowledge about frequent 
expression of AR in Paget's disease could lead to the development of a new 
adjuvant therapy, particularly in patients with recurrent disease.