Probably benign breast masses at US: Is follow-up an acceptable alternative to biopsy?

Purpose: To retrospectively determine whether nonpalpable solid breast masses that were partially or completely obscured at mammography and diagnosed as probably benign only at ultrasonography ( US) can be safely managed with followup. Materials and Methods: The local ethics committee approved this study; informed consent was not required. In 409 women, 448 nonpalpable solid masses were identified and classified as probably benign at US; at mammography these masses were either partially or completely obscured by dense fibroglandular tissue. Of the 448 masses, 445 were followed up, while biopsy was performed after initial imaging in the remaining three. False- negative rates, negative predictive values ( NPVs), and exact 95% confidence intervals ( CIs) were calculated. Results: Of the 445 masses, 442 remained stable at follow- up ( range, 2 - 5 years; mean, 3.3 years). Two masses increased ( fibroadenomas at biopsy). One mass became palpable, and cancer was diagnosed at biopsy. The three masses in which initial biopsy was performed were fibroadenomas. The false- negative rate was 0.2% ( one of 448; NPV, 99.8%; 95% CI: 0.0%, 1.23%). Conclusion: Follow- up US appears to be an acceptable alternative to biopsy for solid masses with benign morphologic features seen at US owing to the extremely high NPV ( 99.8%). (c) RSNA, 2007.