We describe the case of a 35-year-old woman who comes to our institute with a palpable lump on her left breast. Clinically the mass was mobile, nontender and with no nipple discharge. Sonography revealed a circumscribed, oval-shaped, and hypoechoic mass, suggestive of a benign lesion. We performed an ultrasound-guided core needle biopsy that demonstrated multiple foci of high-grade (G3) ductal carcinoma in situ arising on fibroadenoma (FA). Subsequently, the patient had surgical excision of the mass with a final diagnosis of triple-negative breast cancer arising on FA. After diagnosis, the patient performs a genetic test that detects the BRCA 1 gene mutation. A review of the literature demonstrated only two cases of triple-negative breast cancer on FA. In this report, we describe another such case.