Winer LK, et al. - The sampling error rate of flat epithelial atypia (FEA) was ascertained and current guidelines recommending excisional biopsy were appraised via retrospectively reviewing consecutive excisional biopsies following image-guided core-needle biopsy identified patients with isolated FEA. Clinical and pathologic parameters were evaluated. Researchers included 25 women with 27 biopsies. Pathologists at a single institution were not consistent regarding the diagnosis of FEA by histologic examination. Observations revealed an 11.1% incidence of upgrade to malignancy with surgical excision of the site in correlation to the diagnosis of FEA as the sole concerning histologic finding on core needle biopsy. A 25% incidence of upgrade to malignancy was observed with surgical excision of a site of FEA when FEA was diagnosed per WHO criteria.