Metaplastic breast carcinoma presenting as benign breast lump

A 38-year-old female presented with the left breast lump for 6 months. Physical examination revealed 11 cm × 7 cm mobile lump in the left breast without any axillary or supraclavicular lymphadenopathy. Mammographically it appeared as benign breast lump (breast imaging reporting and Data System-II). Fine needle aspiration cytology and Tru-cut biopsy were not able to differentiate between benign or malignant nature of this breast lump. For better characterization of this lesion, lumpectomy was performed, which revealed malignant tumor with squamous differentiation along with areas of ductal carcinoma in situ and the inferior margin was not free. For proper locoregional control, left modified radical mastectomy was performed. Postoperative period was uneventful. Final biopsy report of the mastectomy specimen was negative for any residual tumor, and axillary lymph nodes were not involved.