The primary objective of this pivotal study is to evaluate the safety and efficacy of FUS treatment of breast fibroadenomas. Our hypothesis is that FUS lesion ablation of a fibroadenoma will have the following results: a. lead to a decrease in lesion cross-sectional area of > 50% on palpation, and >65% in lesion volume as measured by MRI (both calculations assume an elliptical shape of the lesion in all 3 dimensions). b. this decrease in size, along with the softening of the treated volume will result in satisfactory clinical results in greater than 50 % of the patients.