Characteristics of ultrasonographic images of ductal carcinoma in situ with abnormalities of the ducts.

Purpose: Although the number of ductal carcinoma in situ (DCIS) cases has increased with the spread of breast cancer screening in Japan, there are very few reports that summarize ultrasound image features of DCIS. The Japan Association of Breast and Thyroid Sonology (JABTS) investigated the incidence of DCIS with masses and non-mass abnormalities and the characteristics of US images in a retrospective, multicenter, observational study (JABTS BC-02 study). The purpose of this report is to clarify the proportion of DCIS with abnormalities of the ducts with each ultrasound finding and the characteristics of US images.

Methods: The JABTS BC-02 study population was comprised of patients who were examined by ultrasonography, underwent surgery, and were histopathologically diagnosed with DCIS at each study site between January 2008 and December 2012. The US images of DCIS and pathology and clinical information were retrospectively collected from 16 institutions in Japan. The US images were evaluated by 22 experts on the Central Image Interpretation Committee of JABTS.

Results: Abnormalities of the ducts were noted in 78 (10.5%) of 705 US images of DCIS. Of the 78 cases, the distribution of abnormalities of the ducts was focal or segmental. The second characteristic was the presence of internal echoes in dilated ducts. All cases were accompanied by intraductal solid echoes, and 40 cases (51.3%) were accompanied by echogenic foci. In addition, intraductal solid echoes were continuous or multiple in 72 cases (92.4%), and the shape of the solid echoes was broad-based and/or irregular in 62 cases (79.5%).

Conclusion: DCIS cases with duct abnormalities on ultrasound were investigated in this study. The important characteristics were as follows: (1) the distribution of ductal dilatation was focal or segmental, (2) solid parts were present in the dilated ducts, (3) the distribution of internal echoes was continuous or multiple, (4) the shape of solid echoes was broad-based and/or irregular, and (5) internal echoes were sometimes accompanied by echogenic foci. Accurate evaluation of these findings may be useful for diagnosing DCIS. Although the duct abnormalities are included in "ASSOCIATED FEATURES" in ACR BI-RADS ATLAS (USA), we emphasize that this concept is very important for understanding US characteristics of DCIS.