Abstract: DUAN Zi-yu, ZHANG Wei, LI A-mei, LV Ya-lin, CHEN Hao, ZENG Xue-si, SUN Jian-fang. Institute of Dermatology, Chinese Academy of Medical Sciences and Peking Union Medical College, Nanjing 210042, China Corresponding author: ZENG Xue-si, Email: xsizeng@163.com 【Abstract】 Objective To investigate the expressions of Na+/H+ exchanger regulatory factor 1 （NHERF1） and β-catenin in extramammary Paget′s disease tissue as well as their significance. Methods Immunohistochemistry was performed to detect the protein expressions of NHERF1 and β-catenin in paraffin-embeded tissue samples from 18 patients with in situ and 22 patients with invasive extramammary Paget′s disease. Results There was a high expression of NHERF1 protein in 18 （81.82%） invasive and 7 （38.89%） in situ extramammary Paget′s disease samples （χ2 = 7.78, P < 0.01）. Statistical differences were observed in the membrane expression rate and cytoplasmic or nuclear expression rate of β-catenin between invasive and in situ extramammary Paget′s disease tissue samples （0 （0/22） vs. 33.33% （6/18）, χ2 = 8.63, P < 0.01; 81.82% （18/22） vs. 44.44% （8/18）, χ2 = 6.08, P < 0.05）. In extramammary Paget′s disease in situ tissue samples, the expression of NHERF1 was negatively correlated with the cytomembrane expression of β-catenin（ρ = －0.488, P < 0.01）, but positively correlated with the cytoplasmic or nuclear expression of β-catenin （ρ = 0.623, P < 0.01）, and there was a negative correlation between the cytomembrane and cytoplasmic or nuclear expression of β-catenin （ρ = －0.572, P < 0.01）. Conclusions There is an abnormal expression of NHERF1 and β-catenin in extramammary Paget′s disease tissue, which may be associated with the initiation, progression, and invasion of primary extramammary Paget′s disease. 【Key words】 Paget′s disease, extramammary; Beta catenin; NHERF1