Papillary lesions of the breast

Abstract

Papillary lesions of the breast comprise a heterogeneous group. These lesions are characterised by the presence of papillary projections of variable length and thickness composed of central fibrovascular cores covered by epithelium. The distinction among intraductal papilloma, papilloma with atypical ductal hyperplasia (ADH) or ductal carcinoma in situ (DCIS), papillary DCIS, and papillary carcinoma can be challenging. An assessment of the presence and distribution of myoepithelial cells in the lesion is one of the most helpful features in arriving at the correct diagnosis. Benign intraductal papillomas and papillomas with atypia (ADH or DCIS) have myoepithelial cells both within and surrounding the involved space. Papillary DCIS and papillary carcinomas lack myoepithelial cells within the papillary proliferation; DCIS retains a myoepithelial cell layer at the periphery and encapsulated and solid papillary carcinomas may lack a peripheral myoepithelial cell layer. Evaluation of the epithelial component is the next step. Benign papillomas have an epithelial component that is heterogeneous with variability in nuclear size, shape and cell placement. Atypia and/or carcinoma usually manifest as a monomorphic proliferation of epithelial cells with low nuclear grade atypia and areas of polarisation. Morphological features and use of adjunctive immunostains to guide diagnosis will be discussed.