Does isolated flat epithelial atypia on vacuum-assisted breast core biopsy require surgical excision?

To determine whether flat epithelial atypia (FEA) found in isolation on large core vacuum-assisted biopsy (CNB) requires surgical excision. After Institutional Review Board approval, pathology reports of all patients who underwent CNB from January 1, 2005 to December 31, 2010 were reviewed. All patients with reports of isolated FEA without other atypia or in situ or invasive carcinoma were identified. Patient age, history, target on imaging, biopsy modality, and residual target post CNB noted. Histology of CNB's (blinded to surgical outcome) and subsequent surgical excisions were reviewed by a dedicated breast pathologist. Only cases with confirmed isolated FEA on review were used for data analysis. Of 2,556 CNB's performed over 6 years, 37 (1.4%) had isolated FEA confirmed on review, comprising our study population. Thirty (81%) had biopsy for calcifications on mammography and 7 (19%) for mass or non-mass like enhancement on magnetic resonance imaging. There were no US guided CNBs that met our inclusion criteria. 29 (78.4%) underwent surgical excision, 6 (16.2%) had imaging follow-up, and 2 (5.4%) were lost to follow-up. Of the 29 with surgery, 2 (6.9%) had "upgrade" to low-grade in situ carcinoma (1 ductal and 1 pleomorphic lobular), 5 (17.2%) had "change in diagnosis" to other atypia (ADH/ALH), 15 (51.7%) had additional FEA and 7 (24.2%) had benign tissue without atypia. Both "upgraded" cases had residual microcalcifications on imaging following CNB. There were no upgrades to invasive cancers. In our study, none of 29 with isolated FEA on CNB had invasive cancer on surgical excision. If there are residual microcalcifications or residual lesion after a CNB that shows isolated FEA, excision is warranted, due to the possibility of other atypia (ADH/ALH [17.2%] or DCIS [5.4%]). If there are no residual microcalcifications following CNB, imaging follow-up as an alternative to surgery may be a reasonable option.