Histological Analysis of Benign Breast Imaging Reporting and Data System Categories 4c and 5 Breast Lesions in Imaging Study

Purpose: The objective of this study was to analyze the histology of breast lesions categorized as Breast Imaging Reporting and Data System (BI-RADS) 4c or 5 breast lesions during the imaging evaluation, but diagnosed as benign during the histological evaluation. Materials and Methods: We retrospectively reviewed 71 breast lesions categorized as BI-RADS 4c or 5 during imaging study, but diagnosed as benign upon histological evaluation. Results: Breast lesions were classified into six groups upon histological analysis: intraductal papilloma (18 cases), inflammatory group (15 cases), fibroepithelial tumor (14 cases), clustered microcalcification (10 cases), minimal histological alteration (10 cases), and adenosis (4 cases). Sclerosis and architectural complexity were associated with most of the biopsies that were morphologically similar to malignancy. Conclusion: Among 71 cases categorized as 4c or 5 during the imaging study, but diagnosed as benign upon histological examination, intraductal papilloma was the most frequently identified histological lesion. These 71 cases exhibited histological characteristics of sclerosis and/or complex/complicated features that should be histologically differentiated from malignancy during evaluation.