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E1421. Duct, Duct…Goose: An Illustrative Guide to Chasing Dilated Ducts
Authors
  1. Daniela Garcia; Mercy Catholic Medical Center
  2. Marion Brody; Mercy Catholic Medical Center
Background
Dilated ducts (DD) are ubiquitous in breast imaging, found in both the screening and diagnostic settings. Normal mammary ducts are not routinely detected on mammography and ultrasound. When dilated, they appear as tubular or tubular branching structures measuring greater than 2 mm in diameter, and greater than 3 mm at the lactiferous sinuses. They may be symmetrically distributed in both breasts (BSDD); asymmetrically distributed in one or both breasts (ADD); or solitary dilated ducts (SDD). The etiology of dilated ducts ranges from benign causes such as duct ectasia to invasive carcinoma. When dilated ducts are associated with typically suspicious findings such as an irregular mass, pleomorphic calcifications, or architectural distortion, biopsy recommendations may be unequivocal. However, findings differentiating benign from malignant causes can be subtle, and in this setting, approaches amongst radiologists often diverge. Many investigations exploring the significance of the more subtle findings have yielded disparate conclusions. Consequently, management recommendations are somewhat ambiguous. A detailed, standardized approach would potentially reduce radiologists’ uncertainty, unnecessary biopsies, overlooked malignancies, and healthcare expenditures.

Educational Goals / Teaching Points
We propose a decision tree for evaluating and managing dilated ducts seen on mammography and ultrasound, based on review of the relevant literature. Through the presentation of multiple cases, we identify key findings that help guide diagnostic decisions.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Bilateral symmetrically DD, and DD that appear stable for at least two years are usually due to duct ectasia and are considered benign (BI-RADS 2). If stability cannot be confirmed, the DD should be further evaluated with targeted ultrasound to assess duct contents. If the ducts contain a solid mass or solid echoes, these will serve as targets for percutaneous biopsy (BI-RADS 4.) If no intraluminal echoes are seen, or the echoes are determined to be mobile by ballotting the area, the finding is probably benign (BI-RADS 3) and may be managed conservatively. Even if there are no solid echoes, however, if there are associated Warning Features such as duct wall thickening or intraluminal calcifications, biopsy is warranted. Similarly, if the DD are new or increasing, or the patient has a nipple discharge or palpable abnormality, MRI should be performed in search of an etiology and a target for tissue sampling.

Conclusion
Evaluation and management of dilated ducts found in breast imaging may be challenging. Discordant study outcomes and somewhat ambiguous recommendations have led to non-standardized approaches. We propose a detailed algorithm, potentially reducing radiologists’ uncertainty, unnecessary biopsies, missed cancers, and healthcare expenditures.