Purpose: The fifth edition of BI-RADS recommends that solitary dilated ducts (SDDs) are assessed as BI-RADS 4 with recommendation for biopsy, however this is not always practiced. This study describes SDD management, malignancy rate, and features associated with malignant/high-risk lesions at a multisite academic center.
Materials and Methods: This retrospective cohort study included all mammogram, ultrasound and MRI exams describing a SDD at our institution between 1/1/2010 and 12/31/2020. Patients were included if they had histological diagnosis, imaging stability, or resolution of findings during follow-up. Features associated with malignant/high-risk histology were analyzed using the Chi-square test.
Results: Fifty-one SDDs in 51 women (mean age 57.1 years) were included. The most common reason for exam was evaluation of a breast symptom (22/51, 43%), nipple discharge being the most common (14/51, 27%). Other reasons included recall from screening mammography (19/51, 37%), history of breast cancer (4/51, 8%), follow-up of another probably benign finding (2/51, 4%), or unspecified (4/51, 8%).
Patients were evaluated with mammography and ultrasound (41/51, 80%), only ultrasound (6/51, 12%), only mammography (3/51, 6%), or MRI (1/51, 2%). All patients had a SDD (mean diameter 4.0 mm), some with an associated intraductal mass (13/51, 25%) or calcifications (2/51, 4%).
Most SDDs were assessed as BI-RADS 4/5 (32/51, 63%), and most were biopsied with ultrasound (26/32, 81%). On biopsy, half were benign (16/32, 50%) and half were high-risk (16/32, 50%). The only BI-RADS 5 lesion, a papilloma with atypia, upgraded to Grade 2 DCIS on excision (malignancy rate 1/51, 2%; positive predictive value-3 1/32, 3%). High-risk lesions included papillomas without atypia (14/15) or with atypia (1/15). Common benign findings included fibrocystic change, stromal fibrosis, and apocrine metaplasia.
Malignant/high-risk lesions were more likely associated with a mass (11/16, 69% versus 2/16, 13%; p = .001) or hypoechoic contents (11/16, 69% versus 5/16, 31%; p = .03) compared to benign lesions. Breast symptoms were not a predictor of malignant/high-risk histology (p = .29).
SDDs assessed as BI-RADS 2 (8/51, 16%) or BI-RADS 3 (11/51, 22%) did not upgrade to malignant/high-risk lesions during follow-up, and none had an associated mass on imaging.
Conclusion: SDDs are rarely described, with a malignancy rate just under 2%. Associated masses or hypoechoic contents predicted malignant/high-risk histology.
Clinical Relevance Statement: Given low malignancy rate and specific imaging predictors, certain SDDs without associated masses or hypoechoic contents may be followed rather than biopsied.
