Differential Diagnosis of Proliferative Breast Lesions.

The correct diagnosis of proliferations within the mammary terminal duct-lobular unit has paramount prognostic and therapeutic implications. Occasionally, the differential diagnosis of compact florid hyperplasia, atypical ductal hyperplasia, and low-grade ductal carcinoma in situ can be quite challenging, with seeming morphologic overlap. This article presents s conceptual and practical understanding of these processes and their impact on subsequent cancer risk, with the intention of assisting the practicing pathologist render accurate and clinically relevant diagnoses for this frequently encountered set of mammary epithelial lesions.