Imaging of Multifocal Adenoid Cystic Carcinoma of the Breast Initially Diagnosed as Adenomyoepithelioma on Core Needle Biopsy: A Case Report.

Adenoid cystic carcinoma (ACC) of the breast is a rare, typically triple-negative malignancy with an indolent course and a biphasic epithelial and myoepithelial histology that can be mistaken for benign or high-risk lesions on core needle biopsy. We describe a 52-year-old woman with two masses at the 4 o'clock position of the right breast, 5 cm and 7 cm from the nipple, in whom ultrasound-guided core needle biopsy of the anterior lesion yielded atypical ductal hyperplasia and stereotactic core needle biopsy of the posterior lesion yielded adenomyoepithelioma. Surgical excision of both sites revealed invasive ACC with foci measuring 24 mm and 4 mm, and after mastectomy without adjuvant therapy, the patient remained free of recurrence for 10 years. This case illustrates that ACC of the breast can be misclassified as atypical ductal hyperplasia or adenomyoepithelioma on core needle biopsy and underscores the importance of radiologic-pathologic correlation and surgical excision of high-risk or discordant lesions.