Introduction: Approximately 25–30% of breast cancers are assumed to be HER-2/neu positive. It is well known that HER-2/neu-positive cancers after treatment with trastuzumab can become HER-2/neu negative. Change in HER-2/neu status from negative to positive following treatment has not been well studied. We describe a patient with inflammatory breast cancer who was initially HER-2/neu negative but became positive after treatment. A 59-year-old postmenopausal white female saw her surgeon for violaceous discoloration of the left breast for 4 months. The surgeon palpated a mass measuring 6 cm in the patient’s left breast. Additionally, there was violaceous discoloration involving two thirds of the breast. Biopsy of the breast mass and skin revealed inflammatory breast cancer. The tumor was estrogen receptor positive, progesterone receptor positive and HER-2/neu negative. The patient was given four cycles of chemotherapy with cyclophosphamide, doxorubicin and docetaxol. She subsequently underwent a mastectomy, excision of the skin over the chest wall and axillary node dissection. Of the axillary lymph nodes, 14/14 were involved. The tumor was still estrogen receptor positive and progesterone receptor positive, but HER-2/neu was 2+ by immunohistochemistry and amplified at 3.3 as detected by fluorescent in situhybridization. The patient received trastuzumab along with chemotherapy followed by radiation therapy and letrozole. She is currently receiving trastuzumab and letrozole in the adjuvant setting and appears to be doing well. Conclusion: A breast cancer which was initially HER-2/neu negative can become positive following treatment. Therefore, re-biopsy may be necessary during the course of treatment of breast cancer to re-assess the HER-2/neu status. This gives the clinician the opportunity to include drugs like trastuzumab and lapatinib in the treatment of patients with a transformation to HER-2/neu-positive cancer.

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