The Clinical Significance of Flat Epithelial Atypia on Core Biopsy: A Single Institution Experience

The clinical significance and management (surgical excision vs. follow-up) of the patients with the diagnosis of Flat Epithelial Atypia (FEA) on Core Needle Biopsy (CNB) varies between institutions, largely due to uncertainty of its biologic potential and its association with more advanced lesions. In this study, we attempted to determine the clinical significance of FEA on CNB based on the upgrade on subsequent excisions, using a single institution experience. Retrospective histopathologic review was performed on CNB with diagnosis of pure FEA for a period of 11 years (January 2010-December 2021) and subsequent excisions by using standardized criteria and precise terminology. Cases with co-existing Atypical Ductal Hyperplasia (ADH) or more advanced lesions (ductal carcinoma in-situ or invasive mammary carcinoma) within the same biopsy cores were excluded from the study. Cases with FEA on CNB without subsequent excisions were also excluded. Our results showed 26.7% upgraded cases of pure FEA to either ADH or in situ carcinoma on the subsequent excisions. Overall, therefore, our findings support surgical excision when FEA is diagnosed on CNB.