Yahaya, James JosephOdida, Michael2021-05-252021-05-252020Yahaya, J. J., & Odida, M. (2020). Primary osteosarcoma of the breast with extensive chondroid matrix in a teenager female patient: the paradoxical diagnosis in breast mastopathy. International Medical Case Reports Journal, 13, 11.DOI: http://doi.org/10.2147/IMCRJ.S233674http://hdl.handle.net/20.500.12661/3206Full text article. Also available at http://doi.org/10.2147/IMCRJ.S233674Non-epithelial tumors of the breast are extremely rare and have an incidence of less than 1%. The most common non-epithelial breast tumor is the phyllodes tumor (PT), which accounts for 61%. Primary osteosarcomas of the breast contribute up to only 12.5% of all breast sarcomas. In young females, osteosarcomas are extremely rare, especially in those without a previous history of primary bone osteosarcoma. A case of a 16-year old female with primary osteosarcoma of the breast (POB) with extensive chondroid matrix involving the left breast is herein presented. This report describes a 16-year old female with neither a previous history of bone osteosarcoma nor family history of breast cancer who was diagnosed with a primary chondroblastic osteosarcoma of the left breast. The mass was shining, warm, firm, and slightly fixed. The excisional biopsy showed a large tumor measuring 11x9x7 cm which was encapsulated, grayish-white, and nodular. Primary osteosarcomas of the breast carry a poor prognosis by being triple negative and because of being the rarest tumors, they pose a challenge in managing the patients due to lack of established treatment modalities.enOsteosarcomaBreastPrimary osteosarcomaBreast tumorsBreast sarcomasChondroblastic osteosarcomaSpindle cell neoplasmsSetaplastic carcinomasMalignant phyllodes tumorMPTArticle