Loss of human epidermal receptor-2 in human epidermal receptor-2+ breast cancer after neoadjuvant treatment: A case report

BACKGROUND: Human epidermal receptor-2 (HER-2) expression has been reported to be discordant between primary tumor and metastatic tissue. CASE SUMMARY: We presented a case diagnosed with the HER-2+ breast cancer patient who exhibited changes in the expression of HER-2 receptors on tumour samples from surgical specimens obtained after neoadjuvant treatment (NAT) compared with initial biopsy. The patient underwent a HER-2-targeted therapy consequently, in spite of HER+ gene loss. After the surgery, the patient subsequently underwent endocrine therapy and radiotherapy. CONCLUSION: Changes in HER-2 expression after NAT should be retested by physicians and pathologists before systemic treatment instead of avoiding further HER-2-targeted therapy, and we will perform immunohistochemical multiple-spot biopsy analyses of other important clinical issues to better define prognosis and tailor subsequent adjuvant therapy.