Upgrade Rate and Imaging Features of Atypical Apocrine Lesions

The purpose of our work was to identify imaging features of atypical apocrine lesions and determine the rate of upgrade to ductal carcinoma in situ (DCIS) or invasive carcinoma at excision after such a diagnosis on percutaneous breast biopsy. From January 1, 2006, through October 8, 2013, a total of 33,157 breast core biopsies were performed at University of Pittsburgh Medical Center. Of those, 58 (0.2%) showed atypical apocrine lesions. For 24, atypical apocrine adenosis (AAA) or atypical apocrine metaplasia (AAM) was the only risk lesion, with no known ipsilateral malignancy, and the results of excision were available. The median patient age was 58 years (range 43-88). Among 24 atypical apocrine lesions (20 AAA and 4 AAM), four (16.7%; 95% confidence interval: 4.7, 37.4) were upgraded at excision: one invasive ductal carcinoma (grade 2, 0.2 cm, estrogen receptor positive, progesterone receptor positive, HER2/Neu negative) and three DCIS (two grade 3, one grade 2). All four upgraded lesions were AAA (20%; 4/20). Twelve AAA were seen as an irregular (n = 9) or circumscribed (n = 3) mass on ultrasound; three masses had calcifications. Six of 20 (30%) AAA were seen on biopsy of calcifications only and calcifications were within two AAA lesions at histopathology. One AAA (1/20, 5%) was asymmetry only, and one (1/20, 5%) a persistently enhancing MR focus. All four malignancies were masses on ultrasound (three irregular, one circumscribed), and three malignancies had calcifications (two coarse heterogeneous, one amorphous). While concordant with an irregular or circumscribed mass on imaging, with or without amorphous or coarse heterogeneous calcifications, AAA merits excision with a 20% upgrade rate to malignancy. Further study of AAM is warranted.