Abstract
Primary osteosarcoma of the breast is a comparatively rare tumor. It has been reported that fibroadenoma or phyllodes tumor might be related in the genesis of the tumor. This time we have experienced a case of osteosarcoma of the breast which was suspected to have some relation to fibroadenoma. The case involved a 69-year-old woman who had noticed tumors of the both breasts for several decades. She was seen at the hospital because her left breast tumor began to enlarge rapidly with pain. On physical examination, an about 12-cm diameter hard mass which had almost replaced the left breast was found. Fine needle aspiration biopsy produced a diagnosis of old fibroadenoma, but a malignant neoplasm was strongly suggested. The tumor was thus resected and the definite diagnosis of osteosarcoma arisen in the breast was made. No distant metastases were identified and no adjuvant chemotherapy was added. The patient has been alive without recurrence as of one year four months after the operation.
