Abstract
Metaplastic breast cancer represents a very rare and histopathologically diverse subtype of breast cancer. It shows neoplastic epithelial differentiation into squamous cells and/or mesenchymal-like components, resulting in its aggressive behavior and poor prognosis compared to other types of breast cancer. Here, we describe the case of a 43-year-old woman diagnosed with metaplastic carcinoma of the breast who presented like any other case of breast lump in the right breast for six months. The tumor had a large size with an ulcerative lesion of the breast. Ultrasound showed heterogeneous echogenicity and lymph node involvement. Surgical resection with axillary lymph node dissection was done. The microscopic examination after tissue processing showed highly pleomorphic tumor cells along with chondromyxoid stroma and osseous differentiation, suggestive of metaplastic breast cancer which was triple-negative for estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2 on immunohistochemistry. The axillary lymph nodes identified were negative for tumor cells. The rarity and aggressive nature of this cancer pose diagnostic challenges and highlight the importance of multidisciplinary approaches for effective management.