Furthermore, about 90% of patients exhibited no difference in the HER2 protein overexpression and ERBB2 gene amplification between primary tumors and corresponded LN metastasis (23), suggesting that HER2’s contribution to the pathogenesis and progression in a subset of metastatic EMPD and implying the possibility that HER2 blockade disrupts the progression of both primary and metastatic lesions of this population. Here, ERBB2 is linked to extramammary Paget disease.