[Papillary tumors of the breast]

The term papilloma applies to benign proliferative epithelial breast lesions with a papillary architecture. The papillae in such lesions contain an arborizing fibrovascular core, glandular surface epithelium and a basal myoepithelial layer. A basement membrane encloses these structures. Papilloma may occur at any site in the ductal lobular system and according to its localization is subdivided into two types: solitary (central) papilloma which are located in the major nipple/subareolar ducts or large segmental ducts and multiple (peripheral) papillomas in cystically dilated terminal ductal lobular units (TDLU). Stromal changes, epithelial metaplasia and/or proliferations and neoplasia may alter the prototypical architecture. In a significant number of papillomas atypia can be identified which have to be classified as atypical proliferates of the ductal type. These lesions must be distinguished from the papillary type of ductal carcinoma in situ. Some 17% of all papilloma are associated with (synchronous) intraductal or invasive carcinoma, but these also act as an indicator for subsequent (metachronous) carcinoma. As a consequence, in minimally invasive biopsy papilloma has to be classified as B3 and usually has to be followed by surgical excision.