[Mammary fibroadenoma showing osseous metaplasia: a case report].

Discussed is a 33-year-old premenopausal woman who noted a mass in her right breast. On palpation, the tumor was determined as being 3.5 x 2.5 cm in size, well circumscribed, of a firm consistency, and freely movable. Mammography showed a well-defined oval lesion which contained a coarse calcification in the upper external quadrant. An ultrasound study revealed a well-defined oval low echoic lesion with a high echoic portion in the internal echo. The tumor was extirpated and a gross inspection found it to be an ordinary fibroadenoma, 3.2 x 2.5 x 1.5 cm in size. Histologically the lesion was a hyalinized fibroadenoma showing osseous metaplasia. A review of the literature has not revealed cases of a benign breast tumors showing an osseous and/or cartilagenous metaplasia. Notable however is that many reports show mammary osteosarcomas as originating from a fibroadenoma. Thus, this tumor also might have possibly developed into a osteosarcoma.