Intraductal papilloma

FIGURE 19.14 A low-power view of an intraductal papilloma with monomorphic cellular proliferation at the bottom right (A). A high-power view demonstrates the presence of DCIS in a papilloma (B). A lack of smooth-muscle myosin heavy chain immunostaining in this morphologically abnormal area confirms the diagnosis of DCIS involving papilloma (C). 

Adenomyoepitheliomas are biphasic tumors that resemble (are a variant of) intraductal papilloma at one extreme and show pure spindle cell myoepithelioma at the other extreme. 

Hill CB, Yeh IT. Myoepithelial cell staining patterns of papillary breast lesions Erom intraductal papillomas to invasive papillaty carcinomas. Am J Clin Pathol. 2005 123 36-44. 

---