We present a woman with consecutively occurring multiple fibroadenomas of thebreast 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 the Hpa II site within exon 1 of the androgen receptor (AR) gene. Estrogen receptor (ER) alpha 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 adenosisfoci and numerous sub-clinical small nodules in the adjacent breast tissue alsosuggested proliferative stimuli throughout the breast. ER alpha protein was expressed only in the nuclei of epithelial cells. The possible influence of ER positive epithelial cells on stromal cell growth is discussed.