Morphogenesis of the papillary lesions of the breast: phenotypic observation

Papillary lesions of the breast are a heterogeneous group of diseases characterised by the presence epithelial proliferation supported by fibrovascular stalks. Normal breast tissue does not show papillary morphology and the mechanisms underlying papillary morphogenesis in breast tumours remain poorly understood. Current clinical evidence indicates an indolent behaviour of malignant papillary breast tumours. Herein, we present some phenotypic features that may explain the development of papillary morphology of breast lesions. Active papillary morphogenesis, which appears to reflect a unique mechanism involving interaction between epithelial and mesenchymal elements, is best appreciated in intraductal papilloma and papillary carcinoma. Morphological evidence suggests papillary morphogenesis during oncogenesis is a dynamic process with variable degrees of papillary differentiation among the same lesion and between primary and metastatic tumours. Secondary papillary-like architecture of non-papillary breast lesions exists. Further studies of the molecular mechanisms underlying papillary morphogenesis in the breast and its association with a better outcome are warranted.