Successful and long-term response to trastuzumab plus paclitaxel combination therapy in human epidermal growth factor receptor 2-positive extramammary Paget's disease: A case report and review of the literature.

A 58-year-old woman with a histologically confirmed diagnosis of vulvar extramammary Paget's disease (EMPD) was referred to our hospital due to locally advanced and relapsed EMPD. The patient had undergone surgical resection three times for relapsed vulvar EMPD over a period of 12 years, but developed locally advanced and unresectable EMPD. As pathological examination indicated that the lesion was positive for human epidermal growth factor receptor 2 (HER2) on immunohistochemical staining, the patient was treated with trastuzumab plus paclitaxel. The primary tumor mass and lymph node metastasis regressed successfully with combined trastuzumab and paclitaxel therapy, and the disease has been stable for >2 years after the initiation of treatment. These observations suggest that HER2 status must be determined in patients with advanced and/or metastatic extramammary Paget's disease and therapy with HER2 inhibitors should be considered as an option for the treatment of HER2-positive EMPD.