Follow‐up of Probably Benign Lesions (BI‐RADS 3 category) in Breast MR Imaging

Abstract: The purpose of our study was to determine the frequency of BI‐RADS 3 lesions in breast MR imaging in a clinical patient population and their frequency of malignancy in follow‐up breast MR imaging. In 44/698 (6.3%) patients with breast MR imaging, 56 lesions were categorized to BI‐RADS 3. These lesions were all not palpable and not detectable at conventional mammography or ultrasound. In follow‐up, lesions were score in complete resolved (CRL), partial resolved (PRL), stable lesions (SL), and progressive lesions (PL). Initial signal enhancement of lesions was coded by color intensity (bright for high, medium for medium, dark for low), the postinitial signal enhancement by color hue (blue for increase, green for plateau, red for wash‐out). In first follow‐up breast MR imaging 23/56 (41%) lesions were PRL, 14/56 (25%) lesions were CRL, 14/56 (25%) lesions remained SL. In one of five PL lesions, histopathology revealed a malignant tumor. In initial breast MR imaging, CRL showed significant fewer high pixels (p = 0.002), medium pixels (p = 0.006) significant more low pixels (p = 0.005) and significant more increase pixels (p = 0.037) than PRL. In a clinical patient population the frequency of malignancy of BI‐RADS 3 lesions in breast MR imaging and their frequency of malignancy are similar to that in conventional mammography. In initial breast MR imaging, complete resolved lesions showed less suspicious contrast kinetics than other lesions. In follow‐up, the increase of lesion size should warrant histopathological diagnosis.     

Imaging and Histopathologic Features of BI‐RADS 3 Lesions Upgraded during Imaging Surveillance

To evaluate imaging and histopathologic differences between screen‐detected benign and malignant upgraded lesions initially assessed as BI‐RADS 3 at diagnostic evaluation. An IRB approved retrospective review of the mammography data base from January 1, 2004 to December 31, 2008 identified 1,188 (1.07%) of 110,776 screening examinations assessed as BI‐RADS 3 following diagnostic evaluation at our academic center (staffed by breast specialists) or our outpatient center (staffed by general radiologists), 1,017 with at least 24 months follow‐up or biopsy. Sixty (5.9%) BI‐RADS 3 lesions were upgraded to BI‐RADS 4 or 5 during imaging surveillance (study population). Prospective reports, patient demographics, and clinical outcomes were abstracted from the longitudinal medical record. Mean patient age was 54.1 years (range 35–85). Lesions consisted of 7 masses, 12 focal asymmetries and 41 calcifications. Fifteen (25%) of 60 lesions upgraded from initial BI‐RADS 3 assessment were malignant (1.47% of total; 15/1,017 BI‐RADS 3 studies). Malignancy rates by upgraded lesion type showed no significant difference: Thirty‐three (73.3%) of 45 benign upgraded lesions were calcifications compared to 8 (53.3%) of 15 malignant upgraded lesions (p = 0.202). Twelve (26.7%) of 45 benign upgraded lesions were masses or focal asymmetries, compared to 7 (46.7%) of 15 upgraded malignant lesions (p = 0.202). Six (85.7%) of 7 malignant upgraded masses/focal asymmetries had no US correlate at initial BI‐RADS 3 assessment compared to 7 (58.3%) of 12 benign upgraded masses/focal asymmetries (p = 0.33). Breast‐imaging specialists interpreted 21 studies, 3 (14.3%) malignant; general radiologists interpreted 39 studies, 12 (30.8%) malignant (p = 0.218). There was no significant difference in malignancy rate among different types of upgraded mammographic lesions, nor depending on subspecialty interpretation versus nonsubspecialist interpretation. Although calcifications made up a majority of upgraded lesions, most were benign, suggesting that decreased surveillance of calcifications may be appropriate.     

BI‐RADS 3 (short‐interval follow‐up) assessment rate at diagnostic mammography: Correlation with recall rates and utilization as a performance benchmark

The purpose of this study was to identify a correlation between the screening BI‐RADS 0 (recall) rates and diagnostic BI‐RADS 3 (short‐interval follow‐up) rates of individual interpreting radiologists, with the goal of utilizing the BI‐RADS 3 rate as an acceptable performance metric in the diagnostic population. A multicenter retrospective analysis of medical audit statistics was conducted on annual radiologist performance data collected over a 14‐year period in a community hospital‐based practice. Mixed regression models were used to estimate the association between screening BI‐RADS 0 and diagnostic BI‐RADS 3 examinations while adjusting for calendar year, annual radiologist screening volume, annual radiologist diagnostic volume, and diagnostic examination indication. A moderate statistically significant positive correlation was established between the screening BI‐RADS 0 rates and Diagnostic BI‐RADS 3 rates (Pearson correlation coefficient + 0.349, P ≤ .001). Furthermore, when utilizing a national benchmark range of 8%‐12% as an acceptable BI‐RADS 0 rate within a screening population, the correlative BI‐RADS 3 assessment rate was demonstrated to be approximately 16%. We propose that this BI‐RADS category 3 rate may represent an additional acceptable performance metric in the diagnostic population. Routine inclusion of an interpreting mammographer's diagnostic BI‐RADS 3 rate in the annual medical audit may help reduce inappropriate and/or excess use of the BI‐RADS 3 category, which may lead to significant potential reductions in follow‐up examinations with their associated healthcare‐related costs, resource expenditure, and induced patient anxiety.     

Misclassification of Breast Imaging Reporting and Data System (BI‐RADS) Mammographic Density and Implications for Breast Density Reporting Legislation

USA states have begun legislating mammographic breast density reporting to women, requiring that women undergoing screening mammography who have dense breast tissue (Breast Imaging Reporting and Data System [BI‐RADS] density c or d) receive written notification of their breast density; however, the impact that misclassification of breast density will have on this reporting remains unclear. The aim of this study was to assess reproducibility of the four‐category BI‐RADS density measure and examine its relationship with a continuous measure of percent density. We enrolled 19 radiologists, experienced in breast imaging, from a single integrated health care system. Radiologists interpreted 341 screening mammograms at two points in time 6 months apart. We assessed intra‐ and interobserver agreement in radiologists'; interpretations of BI‐RADS density and explored whether agreement depended upon radiologist characteristics. We examined the relationship between BI‐RADS density and percent density in a subset of 282 examinations. Intraradiologist agreement was moderate to substantial, with kappa varying across radiologists from 0.50 to 0.81 (mean = 0.69, 95% CI [0.63, 0.73]). Intraradiologist agreement was higher for radiologists with ≥10 years experience interpreting mammograms (difference in mean kappa = 0.10, 95% CI [0.01, 0.24]). Interradiologist agreement varied widely across radiologist pairs from slight to substantial, with kappa ranging from 0.02 to 0.72 (mean = 0.46, 95% CI [0.36, 0.55]). Of 145 examinations interpreted as “nondense” (BI‐RADS density a or b) by the majority of radiologists, 82.8% were interpreted as “dense” (BI‐RADS density c or d) by at least one radiologist. Of 187 examinations interpreted as “dense” by the majority of radiologists, 47.1% were interpreted as “nondense” by at least one radiologist. While the examinations of almost half of the women in our study were interpreted clinically as having BI‐RADS density c or d, only about 10% of examinations had percent density >50%. Our results suggest that breast density reporting based on a single BI‐RADS density interpretation may be misleading due to high interradiologist variability and a lack of correspondence between BI‐RADS density and percent density.     

Breast Nonmass Enhancement Detected with MRI: Uility and Lesion Characterization with Second‐Look Ultrasonography

The purpose of this study was to verify the utility of second‐look ultrasonography (US) in evaluating nonmass enhancement (NME) lesions detected on breast magnetic resonance imaging (MRI) by analysing its correlation and imaging features. From July 2008 to June 2012, 102 consecutive MRI‐detected NME lesions were subsequently evaluated with US. Lesions were evaluated according to the established Breast Imaging Reporting and Data System (BI‐RADS) lexicon. The correlation between MRI‐detected NME lesion characteristics, lesion size, histopathological findings and features at second‐look US were analysed. Second‐look US identified 44/102 (43%) of the NME lesions revealed by MRI. A US correlate was seen in 34/45 (76%) malignant lesions compared with 10/57 (18%) benign lesions (p < 0.0001). The likelihood of malignancy was significantly higher for NME lesions with a US correlate than lesions without: 34/44 (77%) versus 11/58 (19%) (p < 0.0001). The malignancy of the 44 (43%) MRI‐detected NME lesions with a US correlate was significantly associated with US lesion margins and BI‐RADS categories (p = 0.001 and 0.002 respectively). Second‐look US of MRI‐detected NME lesions is useful for decision‐making as part of the diagnostic workup. Familiarity with the US features associated with malignancy improves the utility of US in the workup of these NME abnormalities.