Both immunohistochemistry and fluorescence in situ hybridization studies of primary and LN metastatic lesions have revealed the HER2 overexpression (HER2 score of 3+ or 2+) in 15–58% of patients with EMPD and that all cases with a HER2 score of 3+ had amplified ERBB2, the gene encoding HER2 (16, 22). Here, ERBB2 is linked to extramammary Paget disease.