Experiences of trastuzumab plus paclitaxel combination therapy in metastatic human epidermal growth factor receptor 2-positive extramammary Paget's disease: Four cases and a review.

Tumor cells in extramammary Paget's disease sometimes overexpress human epidermal growth factor receptor 2 (HER2). Several case reports indicated successful response to HER2 inhibitor in patients with HER2-positive metastatic extramammary Paget's disease. However, these were single-case reports, and most cases were evaluated only by immunohistochemistry and treated with HER2 inhibitor monotherapy.