目的探讨乳腺原发性骨肉瘤的临床病理学特征、鉴别诊断、治疗及预后。方法应用光镜观察及免疫组化染色对1例乳腺原发性骨肉瘤进行临床病理分析,并复习相关文献。结果患者临床症状和辅助检查无特异性,镜下示:大部分区域见肿瘤性骨样组织,骨样组织被瘤细胞包绕,瘤细胞呈梭形、卵圆形、多边形,并可见破骨细胞样多核巨细胞。免疫组化:瘤细胞vimentin(+)、破骨样多核巨细胞CD68(+),ER、PR、Her-2及上皮标记均(-)。结论乳腺原发性骨肉瘤极罕见,确诊需依据临床病理形态学特点及免疫组化,治疗以手术为主,可选用单纯乳房切除或改良根治术。 Objective To investigate the clinicopathological features, differential diagnosis, treatment and prognosis of primary osteosarcoma in breast. Methods One case of primary osteosarcoma of breast was analyzed by light microscopy and immunohistochemical staining, and the related literatures were reviewed. Results The patient’s clinical symptoms and laboratory tests were nonspecific. Microscopically, most of the tumors were found in the tumorous bone-like tissues. The bone-like tissues were surrounded by the tumor cells. The tumor cells were fusiform, oval and polygonal, Cytoplasmic multinucleated giant cells. Immunohistochemistry: The tumor cells vimentin (+), osteoclast-like multinucleated giant cells CD68 (+), ER, PR, Her-2 and epithelial markers were (-). Conclusions Primary osteosarcoma of the breast is very rare. The diagnosis should be based on the clinicopathological features and immunohistochemistry. The treatment is mainly based on the operation. Simple mastectomy or modified radical mastectomy may be used.