Significant efficacy of trastuzumab emtansine in HER2-positive relapsed mammary Paget’s disease: a case report and literature review

A 58-year-old female patient was referred to our hospital due to a left chest wall relapse after a surgical excision 20 years ago. She received taxanes and trastuzumab regimen treatment for chest wall recurrence in 2019, but subsequently discontinued the treatment due to personal reasons. Her left chest wall was ruptured and oozed with pus when she came to our hospital. The tumor biopsy confirmed HER2 (human epidermal growth factor receptor 2) positive breast cancer metastasis, and she was diagnosed with mammary Paget’s disease (MPD). The skin symptoms regressed successfully with Trastuzumab Emtansine (T-DM1) treatment. This case suggests that the T-DM1 regimen is effective in relapsed MPD with HER2-positive and anti-HER2 targeted therapy should be considered as an option for the treatment of HER2-positive MPD.