Consecutively occurring multiple fibroadenomas of the breast distinguished from phyllodes tumors by clonality analysis of stromal tissue

We present a woman with consecutively occurring multiple fibroadenomas of the breast distinguished from phyllodes tumor by clonality analysis of stromal tissue. Fifty-three masses developed in her right breast in an 11.5 year period since first onset. A clonality analysis, performed by polymerase chain reaction (PCR), focused on theHpa II site within exon 1 of the androgen receptor (AR) gene. Estrogen receptor (ER) α immunohistochemistry was performed with a specific polyclonal antibody against the hormone binding domain of the protein. Since all of the nodules were polyclonal in stromal tissues, they were hyperplastic rather than true neoplasms such as phyllodes tumors. The co-existence of abundant adenosis foci and numerous sub-clinical small nodules in the adjacent breast tissue also suggested proliferative stimuli throughout the breast. ER α protein was expressed only in the nuclei of epithelial cells. The possible influence of ER positive epithelial cells on stromal cell growth is discussed.