Mammary duct ectasia represents a benign condition characterized by the dilatation of the mammary ducts. The diagnosis can be clinically challenging due to its complex and diversified symptoms, but also because in some cases it can mimic breast cancer.
Furthermore, inappropriate diagnosis or treatment of this condition may result in persistent symptoms or recurrent onset and persistent symptoms. Therefore, a proper approach is to employ imaging methods to establish a diagnosis of mammary duct ectasia – primarily mammography, galactography, ultrasound, and magnetic resonance imaging.
On mammography (which provides X-ray images of the breast), mammary duct ectasia is seen as one or more tubular structures that are oriented to the nipple. If fibrosis predominates, then the lesion may be visualized as an ill-delimited mass, akin to breast carcinoma.
If calcifications are present, they are typically elongated and coarse, pointing towards the nipple (although some of them can also be round with central radiolucency). Most of them are easily recognized as benign in nature, especially if they are positioned bilaterally.
In general, calcifications found in mammary duct ectasia are of wider caliber and higher density than calcifications linked to malignant changes. However, if they are very small, they can resemble microcalficications of an intraductal carcinoma, warranting a biopsy.
Non-calcifying mammary duct ectasia in women with nipple discharge is better evaluated by galactography, which is a technique that uses a retrograde injection of water-soluble radiopaque contrast into the breast duct system. Nevertheless, this imaging method is not indicated for bilateral nipple discharge, nor for discharges from multiple orifices.
Ultrasound is quickly entering the clinical practice as the new reference method for evaluation of suspected mammary duct ectasia and other ductal diseases. Even though the appearance of ducts can vary substantially between patients (and even within areas of the same breast), they are visualized as tubular structures generally wider at the level of the nipple with peripheral arborization.
Sonographic appearance of mammary duct ectasia depends on the stage of the disease, but also on the content of the dilated ducts. Generally, it presents with dilated and fluid-filled subareolar ducts that contain moving echogenic debris without mass, which often mimics an intraductal tumor (most notably papilloma).
Similarly, magnetic resonance technology has become entrenched as a diagnostic standard for mammary diseases. Albeit plain magnetic resonance scan does not provide any pathognomonic findings related to mammary duct ectasia, T2-weighted imaging (one of the basic pulse sequences of magnetic resonance) and diffusion-weighted imaging can reveal the morphology, location, and size of these lesions.
Cytology is a useful option when clinicians are confronted with a nipple discharge of unknown origin. If mammary duct ectasia is the underlying cause, cytological findings usually encompass isolated and scattered epithelial cells, amorphous material, scarce macrophages, and some red blood cells.
The most important finding is that final diagnosis is negative for malignancy. Still, sometimes certain diagnostic difficulties arise as a result of the suspicious clinical and abnormal mammographic findings; in such cases, fine needle aspiration cytology together with immunocytochemistry might allow clear-cut classification in the adequate clinical setting.