Extramammary Paget disease (EMPD) is a rare cutaneous adenocarcinoma that usually is of epidermal origin and shows glandular differentiation and that is treated by wide local excision depending on the disease extent. For widely metastatic disease, however, a standard treatment remains to be established. Similar to breast cancer, EMPD has been found to overexpress human epidermal growth factor receptor 2 (HER2) or hormone receptors (HRs). Whereas HER2-directed therapy was recently shown to be effective for HER2-positive EMPD, the potential role of endocrine therapy for HR-positive EMPD has remained unknown. We here report a case of metastatic EMPD with HR positivity that was successfully treated with the selective estrogen receptor modulator tamoxifen. This first-line treatment of systemic metastasis resulted in durable tumor regression for > 20 months without any treatment-related toxicities. This is the first report to reveal the promise of tamoxifen as a safe and effective treatment for HR-positive metastatic EMPD.
Keywords: Extramammary Paget disease (EMPD); Hormone receptor; Molecular targeted therapy; Tamoxifen.
© 2021. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.