This investigation aimed to assess HER2 expression heterogeneity between primary tumors and metastatic lymph nodes (LNs) in patients with advanced EMPD and to assess the prognostic value of HER2 expression and other pathological factors in determining the therapeutic value of HER2 targeting.<h4>Methods</h4>We included 170 patients diagnosed with primary EMPD. The gene discussed is ERBB2; the disease is extramammary Paget disease.