Assessing intraductal proliferations in breast core needle biopsies

Intraductal proliferations of the breast comprise a heterogeneous group of epithelial proliferations confined to the ductal and lobular system of the breast parenchyma. The correct interpretation and categorization of such lesions can be challenging, especially on core needle biopsy, but are critical for appropriate clinical management as this determines whether surgical excision is or is not required. In this paper we aim to review the histologic criteria and terminology for the spectrum of intraductal proliferative lesions. We will discuss the key morphologic features and diagnostic mimics of usual ductal hyperplasia, atypical ductal hyperplasia, and ductal carcinoma in situ, and provide practical guidelines for interpretation in core needle biopsy specimens.