A Case of Primary Extraskeletal Osteosarcoma of the Breast

Abstract

Primary extraskeletal osteosarcoma of the breast is extremely rare and has poor prognosis. A 51-year-old woman noticed that the tumor in her left breast had grown rapidly. She had a history of breast cancer on the right 5 years ago. At the same time, a fibroadenoma was detected in her left breast, which was confirmed histopathologically. Re-biopsy specimen analysis revealed that the tumor was probably borderline to malignant phyllodes tumor, metaplastic carcinoma, or stromal sarcoma. The tumor enlarged rapidly during subsequent examinations ; therefore, left mastectomy with sentinel node biopsy was performed as a semi-emergency operation. Pathologically, no epithelial cells were observed in the tumor ; however proliferation of spindle cells and osteoid formations were found. The tumor cells tested positive for Vimentin and CD68 immunohistochemically. A final diagnosis of primary extraskeletal osteosarcoma of the breast was made. The patient underwent adjuvant methotrexate, adriamycin, and cisplatin therapy. The patient has survived with no recurrence reported for 19 months since the operation.