Fibroepithelial lesions (FELs) are a common histologic finding on core needle biopsy (CNB) of the breast. Fibroepithelial lesions include fibroadenoma and phyllodes tumor, which can be difficult to distinguish with an initial CNB. An institutional experience was reviewed from February 12, 2001, to January 4, 2007, to determine the safety of selective rather than routine excision of FELs and to determine the factors associated with upgrading diagnosis of FELs to phyllodes tumors without definitive phyllodes tumor diagnosis by CNB. Of 313 patients, 261 (83%) with FELs diagnosed by CNB received observation with long-term follow-up (mean, 8 years). Of the observed patients, 3 (1%) were diagnosed with phyllodes tumor on follow-up. Eighteen of 52 patients (35%) who received excision had an upgrade of diagnosis to phyllodes tumor. Sensitivity and specificity of the pathologist's comment of concern for phyllodes tumor on a CNB demonstrating FELs without definitive phyllodes tumor diagnosis were 82% and 93%, respectively. Our policy of selective excision of FELs without definitive phyllodes tumor diagnosis resulted in safe avoidance of many surgical procedures.