The purpose of our study was to describe the imaging findings in adenoid cystic carcinoma (ACC) of the breast, with pathologic and clinical correlation.We retrospectively searched our surgical database from January 1994 through December 2008 for cases of pathologically proven ACC of the breast. Of approximately 15,000 breast biopsies, 11,250 were malignant. Eleven cases of ACC (0.1% of all malignancies), all with imaging available for review, were included in the study.Mammographically (n = 10), tumors appeared as developing asymmetric densities or irregular masses. Sonographically (n = 9), they appeared as irregular, heterogeneous, or hypoechoic masses with minimal vascularity on color Doppler imaging. MRI (n = 5)--because of better soft-tissue contrast and dedicated, multiplanar breast sequences--helped show the extent of the tumor, particularly if dense breast tissue obscured the mass on CT. Two cases with subtle sonographic findings were better delineated on MRI because of tumor enhancement. The solid variant showed increased signal intensity on T2-weighted imaging. ACC showed variable enhancement kinetics ranging from persistent enhancement to washout kinetics in the larger lesions. On molecular breast imaging (n = 1), the tumors showed avid uptake of radiotracer but did not always show activity on PET (n = 1). CT (n = 2) showed areas of rapid, nodular enhancement.Recognition of ACC is important to avoid delay in diagnosis because this tumor has a good prognosis with rare metastases to axillary lymph nodes. Axillary nodal sampling by fine-needle aspiration or core biopsy is rarely indicated.