Background: Extraskeletal osteosarcomas are rare, malignant mesenchymal neoplasms of soft tissues. They account for less than 1% of the soft tissue sarcomas. Primary breast osteosarcomas are extremely rare. They are often aggressive with poor prognosis and often pose diagnostic dilemma for the surgeon. We present a case along with the relative review of the literature. Materials and Methods: Demographics and imaging studies of the selected patient were collected. Written consent was obtained. The literature review included only articles cited on PubMed. The keywords used were “primary breast osteosarcoma”, “breast cancer” and “soft-tissue sarcoma”. Results: A 74-year-old woman presented with a large mass with hard texture on her right breast. She noticed this mass 2 months prior admission. Mammography and breast ultrasound showed a well-circumscribed round-shaped calcified mass on the upper central portion of the right breast. No clinically enlarged lymph nodes were detected in the axilla. Initially a benign calcified fibroadenoma was considered propable. However, the mass was enlarged in less than two months. Due to the tumors’ growth a lumpectomy was performed. The pathological examination revealed breast osteosarcoma with negative margins. Given the negative staging, tumor board recommended adjuvant chemotherapy and the patient had reached 4-year survival but died due to non-disease related issues. Conclusion: Primary breast osteosarcoma is an extremely rare clinical entity. A preoperative diagnosis is challenging. Due to the rarity of the disease, its clinical features range and treatment modalities remain highly personalized. High suspicion and proper treatment ensure early diagnosis and optimal prognosis.