Papillary neoplasms of the breast: Practical diagnostic updates and emerging concepts

Papillary breast neoplasms comprise a heterogeneous spectrum ranging from benign intraductal papillomas to invasive carcinomas and remain among the most diagnostically challenging breast lesions because of overlapping morphology, variable myoepithelial cell (MEC) distribution, sampling limitations, the mismatch between conventional histological criteria and clinical behaviour, and evolving concepts of stromal invasion. Recent advances, including the sixth edition of the WHO Classification of Breast Tumours, have refined the classification of papillary neoplasms, particularly encapsulated papillary carcinoma (EPC), and solid papillary carcinoma (SPC). However, important diagnostic and management challenges remain, particularly in distinguishing overlapping papillary neoplasms from one another and from their numerous morphological mimics. This narrative review provides a practical, evidence-based diagnostic framework that integrates morphology, immunohistochemistry, radiological-pathological correlation, and emerging biological concepts. Particular emphasis is placed on contemporary concepts of invasion, recognising papillary neoplasia as a biological continuum rather than discrete entities, and on the limitations of applying conventional histological criteria beyond the biological context in which they were originally established. Recent developments in the classification of invasive papillary neoplasms, mixed papillary lesions, staging challenges, papillary lesion mimics, and interpretation of core needle biopsies are reviewed. Throughout, an integrated, context-dependent approach is advocated, emphasising the interpretation of morphology within its biological and clinicopathological context rather than reliance on isolated diagnostic criteria. This review provides a practical, biologically informed framework for the contemporary classification, diagnosis, and management of papillary breast neoplasms.