Clinical history: 64 year old female with nipple discharge.
What is the most probable diagnosis?
Intraductal papilloma with atypical ductal hyperplasia (atypical papilloma)
The biopsy shows a papillary lesion expanded by a monomorphic epithelial proliferation in a cribriform and focally solid pattern, consistent with atypical ductal hyperplasia (ADH) or focal low grade ductal carcinoma in situ (DCIS). The lesion itself is less than 3 mm in size. Immunohistochemical studies with ADH5 show the presence of myoepithelial cells (brown stain) associated with the papillary lesion, but absent in the foci of ADH/DCIS. ADH5 is a multiplex immunohistochemical cocktail consisting of CK5, CK7, CK14, CK18, and p63. CK14, CK5 and p63 is indicated by brown staining (i.e. myoepithelial cells), while CK7 and CK18 stain red (low molecular weight keratins).
Atypical papilloma, or papilloma with atypia, are intraductal papillomas that exhibit monotonous areas of epithelial proliferation that fulfill the combined architectural and cytologic criteria for the diagnosis of ADH or low-grade DCIS within a benign papilloma, but are less than 3 mm in size. If the size of the atypical focus was >3mm, then this would be diagnosed as DCIS involving a papilloma. Also, if the atypia within the papilloma was intermediate or high grade, this would be diagnosed as DCIS involving a papilloma regardless of the extent.