Clinical history: 52 year old female with a 0.7 cm mass in the 9:00 position of the right breast detected by mammography. Ultrasound guided core needle biopsies.
What is the diagnosis?
Intraductal papilloma with apocrine metaplasia.
Papillomas are lesions of true ducts. They are most common in the perimenopausal age group and can present as nipple discharge or a palpable mass.
Solitary papillomas are often located near the nipple-areolar complex and multiple papillomas are often located peripherally. An intraductal papilloma confers 1.5-2.0 times the lifetime risk of breast carcinoma. Definitive management consists of surgical excision.
Microscopically they consist of multiple branching papillae lined epithelium with two cell layers (luminal epithelium and basal myoepithelial layer). The luminal epithelium can undergo proliferative changes similar to the rest of the breast and papillomas may therefore contain areas of usual or atypical ductal hyperplasia, apocrine or squamous metaplasia.
When evaluating a papillary lesion in the breast the differential diagnosis includes intraductal papilloma, papilloma with atypia (focal involvement by ADH or DCIS), papillary DCIS, encysted non-invasive papillary carcinoma, invasive papillary carcinoma and solid papillary carcinoma. Myoepithelial markers are often required to distinguish these diagnostic entities.