Intraductal proliferations of the breast: a review of histologic criteria for atypical intraductal hyperplasia and ductal carcinoma in situ, including apocrine and papillary lesions.

The proliferation of intraductal mammary epithelium forms a continuum that begins with intraductal hyperplasia and ends with ductal carcinoma in situ. Atypical intraductal hyperplasia is the midpoint between the benign and malignant poles of this proliferative continuum. By defining the histological criteria for atypical intraductal hyperplasia, distinction from ordinary intraductal hyperplasia and the noncomedo forms of ductal carcinoma in situ becomes easier. Histopathologic criteria for atypical intraductal hyperplasia, ductal carcinoma in situ, and intraductal hyperplasia and their relative risks for the development of invasive breast carcinoma are reviewed. Related topics of intraductal apocrine and papillary proliferative lesions also are discussed.