Fibroadenomas are the most common benign breast tumors in women under 30. Unlike their malignant counterparts, relatively molecular profiling has been done on fibroadenomas. Here we performed gene expression profiling on ten fibroadenomas in order to better characterize these tumors. Through targeted amplicon sequencing, we have found that six of these tumors have MED12 mutations. We show that the MED12 mutations, among others, are associated with activated estrogen signaling, as well as increased invasiveness through upregulation of ECM remodelling genes.