Classical Lobular Carcinoma In Situ Arising From an Intraductal Papilloma of the Breast: A Case Report.

Intraductal papilloma of the breast is a benign, mass-forming, proliferative lesion with a papillary architecture confined within a duct. Lobular neoplasia can rarely arise from an intraductal papilloma of the breast. In this article, we report the morphologic features of a rare case of classical LCIS (lobular carcinoma in situ) arising from an intraductal papilloma in a 76-year-old woman. The monomorphic dyscohesive cells were present between the myoepithelial and luminal epithelial layer in the periphery of the papilloma. These cells partially obliterated the spaces between the papillae forming solid sheets. The monomorphic dyscohesive cells showed lack of E-cadherin expression and uniform staining for estrogen receptor. We review the histologic differential diagnosis and stress the importance of correct classification to ensure optimal care for patients. We also propose a new criterion for the distinction of lobular neoplasia within a papilloma.