Imaging approaches to diagnosis and management of common ductal abnormalities.

Ductal disease is an important, often overlooked, and poorly understood issue in breast imaging that results in delays in diagnosis and patient care. The differential diagnosis for an intraductal mass is broad and includes inspissated secretions, infection, hemorrhage, solitary or multiple papillomas, and malignancy. Each breast is composed of eight or more ductal systems, with most disease arising in the terminal ductal-lobular unit. Imaging evaluation of the ductal system usually entails a combination of mammography, galactography, ultrasonography (US), and in some cases magnetic resonance (MR) imaging. The most common finding with all modalities is ductal dilatation with a focal or diffuse abnormality. Benign diseases of the ducts include duct ectasia, blocked ducts, inflammatory infiltrates, periductal mastitis, apocrine metaplasia, intraductal papillomas, and papillomatosis. Malignant diseases of the ducts include ductal carcinoma in situ, invasive ductal carcinoma, and Paget disease. Most commonly performed with US or MR imaging guidance, percutaneous biopsy methods are helpful in diagnosis and management of ductal findings. Because most findings are smaller than 1 cm, located within a duct, and thus sometimes not visible after a single pass, vacuum-assisted devices help improve the accuracy of sampling.