Human Epidermal Growth Factor Receptor 2 (HER2/Neu)-Positive Ovarian High-Grade Serous Carcinoma Metastasizing to the Breast: A Case Report.

Metastasis to the breast from malignancies is rare and often poses a diagnostic challenge due to its clinical and radiologic similarity to primary breast cancer. We report the case of a 47-year-old woman who presented with abdominal discomfort, a palpable abdominal mass, and bilateral inguinal lymphadenopathy. Imaging and biopsy revealed high-grade serous carcinoma of Müllerian origin with human epidermal growth factor receptor 2 (HER2/neu) overexpression, which had metastasized to the breast and right axillary lymph nodes. She was treated with a combination chemotherapy regimen of Taxotere, carboplatin, trastuzumab, and pertuzumab (TCHP). This case underscores the importance of distinguishing metastatic involvement of the breast from primary breast cancer to ensure appropriate treatment and management.