A case of phyllodes tumor of the breast with a lesion mimicking fibroadenoma.

We report a case of phyllodes tumor (PT) with multiple lesions partly mimicking fibroadenoma (FA). A 43-year-old woman was referred to our institute because of a left breast mass which was diagnosed as FA clinically. During the follow-up, the mass gradually enlarged and excisional biopsy was performed to rule out malignant lesion. On histological examination, the tumor consisted of three different components; a lesion diagnosed as FA, another lesion as benign PT, and the other lesion as borderline PT. Finally, the tumor was diagnosed as borderline PT. Stromal cellularity may vary from area to area in any given PT. If there are some disagreements among the findings of imagings and cytology for the diagnosis of FA, as was seen in our case, the possibility of coexistence of PT should be considered.