Solitary dilated duct identified at mammography: outcomes analysis

The purpose of this study is to review the clinical and pathologic outcomes for cases of solitary dilated duct identified at mammography.

For all screening mammography examinations during a 22-year period and all diagnostic mammography examinations during the last 10 of these years, the radiologists recorded the principal finding of each abnormal mammographic examination during image interpretation. Only examinations with the recorded finding of solitary dilated duct were studied. We examined radiology records to determine imaging follow-up and pathology records to determine histologic diagnosis, and we performed linkage with our regional tumor registry to identify cancers not biopsied at our institution.

The finding of solitary dilated duct was recorded for nine (0.0038%) of 235,209 consecutive screenings and for 12 (0.041%) of 29,267 consecutive diagnostic mammography examinations. Five screening and five diagnostic cases were stable at follow-up (minimum interval, 2 years) and did not undergo biopsy; tumor registry linkage showed no subsequent cancer diagnosis. Biopsy was performed for four (44%) of nine screening and seven (58%) of 12 diagnostic cases. One cancer each (ductal carcinoma in situ) was identified from the screening and diagnostic populations, yielding positive predictive values of 11% (1/9) and 8% (1/12), respectively.

Solitary dilated duct is a rare mammographic finding, this series being the largest reported to date. Although few cases are studied, solitary dilated duct appears to have a greater than 2% likelihood of malignancy, sufficiently high to suggest that a suspicious (BI-RADS 4a) assessment may be appropriate.