Atypical apocrine adenosis diagnosed on breast core biopsy: implications for management

Apocrine adenosis (AA) and atypical apocrine adenosis (AAA) are uncommon findings in breast biopsies that may be misinterpreted as carcinoma. The data from long-term follow up studies of open biopsies suggest that AAA is not a high-risk or precursor lesion. The clinical significance and risk implications of AAA diagnosed on core biopsy are not well established. The goal of this study was to determine the frequency of carcinoma in excision specimens after a core biopsy diagnosis of AA or AAA. We identified 34 core biopsies of AA (22) and AAA (12) performed between 1996 and 2014. The mean age at diagnosis was 60 years. The most common indications for core biopsy were calcifications (11), a mass or density (18), and a mass or density with calcifications (3). Two cases were detected on magnetic resonance imaging (MRI) studies. Available pathology reports and slides were reviewed, and surgical excision findings were correlated with core biopsy diagnoses. Of the core biopsies with AA or AAA, 7 also contained atypical ductal or lobular hyperplasia (AH) and 4 contained ductal carcinoma in situ or invasive carcinoma. In the absence of coexisting AH or carcinoma in the initial core biopsy specimen, none of the surgical excision specimens after a diagnosis of AA (2) or AAA (7) contained ductal carcinoma in situ or invasive carcinoma. AAA by itself is an uncommon core biopsy diagnosis that may not require surgical excision.