Sarcomas of the breast are relatively rare neoplasms accounting for less than 1% of breast malignancies [
1]. Histological examination shows the majority to be fibrosarcomas, malignant fibrous histiocytomas and undifferentiated high grade sarcomas [
2]. Tumors of the breast containing bone and cartilage can be divided into four groups: intra-ductal papilloma with stromal metaplasia; cystosarcoma phyllodes; stromal sarcoma; and adenocarcinoma with metaplasia [
3]. The mechanism of formation of bone and cartilage differs in the above noted groups. In the lesions classified as adenocarcinoma with metaplasia, there is metaplasia of the epithelial cells to cartilage or bone while in the cystosarcoma and intra-ductal papilloma there is metaplasia of the stromal cells [
4]. Pathological bone formation in the breast tissue may be the result of inter-membranous ossification and the marrow is not observed [
5,
6]. Extra-osseous osteosarcomas have also been reported in thyroid gland, kidney, urinary bladder and uterus [
7]. Overall, mammary osteosarcomas are biologically aggressive tumors characterized by early recurrences and hematogenous metastasis, frequently to the lungs [
8]. Optimal management should include total excision of the neoplasm with an adequate margin for control of local disease. A simple mastectomy may be indicated to ensure complete excision of large tumors with cryptically infiltrative margins [
2]. Axillary lymph node dissection is not indicated in the setting of clinically negative nodes. Although the role of adjuvant therapy is unclear, several studies involving a small number of patients suggest that adjuvant chemotherapy may be of value in patient management [
8]. Distinguishing metaplastic carcinoma and carcinosarcoma from osteosarcoma of the breast is important, because the former necessitates treatment as primary breast cancer. Finally, although the breast is an unusual site of metastases, it is necessary to exclude the possibility of a metastatic lesion, as well as primary osseous osteosarcoma, before establishing the diagnosis as osteosarcoma of the breast.