Comparison of False-Positive Versus True-Positive Findings on Contrast-Enhanced Digital Mammography

Abstract

BACKGROUND. Contrast-enhanced digital mammography (CEDM) has been shown to outperform standard mammography while performing comparably to contrast-enhanced MRI. OBJECTIVE. The purpose of our study was to compare imaging characteristics of false-positive and true-positive findings on CEDM. METHODS. This retrospective study included women who underwent baseline screening CEDM between January 2013 and December 2018 assessed as BI-RADS category 0, 3, 4, or 5 and who underwent biopsy with histopathologic diagnosis or had a 2-year imaging follow-up. Lesion characteristics were extracted from CEDM reports. A true-positive finding was defined as a lesion in which biopsy yielded malignancy. A false-positive finding was defined as a lesion in which biopsy yielded benign or benign high-risk pathology or in which 2-year imaging follow-up was negative. RESULTS. Of 157 patients (median age, 52 years), 24 had a total of 26 true-positive lesions, and 133 had a total of 147 false-positive lesions. Of the 26 true-positive lesions, one (4%) exhibited only a mammographic finding on low-iodine images, 13 (50%) exhibited only a contrast finding on iodine images, and 12 (46%) exhibited both a mammographic finding on low-energy images and a contrast finding on iodine images. A true-positive result was more likely (p = .02) for lesions present on both low-energy images and iodine images (31%) than on low-energy images only (4%) or iodine images only (12%). Among lesions present on both low-energy and iodine images, a true-positive result was more likely (p < .001) when the type of mammographic finding was an asymmetry (46%) or calcification (80%) than a mass (11%) or distortion (0%). A true-positive result was more likely (p = .01) among those with, versus those without, an ultrasound correlate (36% vs 9%) and also was more likely (p = .02) among those with, versus those without, an MRI correlate (18% vs 2%). Of 25 false-positive calcifications, 24 had no associated mammographic enhancement; of five true-positive calcifications, four had mammographic enhancement. CONCLUSION. A low-energy mammographic finding with associated enhancement or a finding with a sonographic or MRI correlate predicts a true-positive result. Calcifications with associated enhancement had a high malignancy rate. Nonetheless, half of true-positive lesions enhanced on iodine images without a mammographic finding on low-energy images. CLINICAL IMPACT. These observations inform radiologists' management of abnormalities detected on screening CEDM.

Keywords: breast cancer; breast screening; contrast-enhanced digital mammography; false-positive.

Fig. 1 —

Flowcharts of study results. CEDM = contrast-enhanced digital mammography, LE = low-energy, US = ultrasound, FU = follow-up, IDC = intraductal carcinoma, ILC = invasive lobular carcinoma, DCIS = ductal carcinoma in situ. A, Flowchart shows results of evaluation for 173 lesions identified on CEDM. B, Flowchart shows results of evaluation for 106 lesions identified only on iodine images. C, Flowchart shows results of evaluation for 39 lesions identified on both iodine and low-energy images. D, Flowchart shows results of evaluation for 28 lesions identified only on low-energy images.

Fig. 1 —

Flowcharts of study results. CEDM = contrast-enhanced digital mammography, LE = low-energy, US = ultrasound, FU = follow-up, IDC = intraductal carcinoma, ILC = invasive lobular carcinoma, DCIS = ductal carcinoma in situ. A, Flowchart shows results of evaluation for 173 lesions identified on CEDM. B, Flowchart shows results of evaluation for 106 lesions identified only on iodine images. C, Flowchart shows results of evaluation for 39 lesions identified on both iodine and low-energy images. D, Flowchart shows results of evaluation for 28 lesions identified only on low-energy images.

Fig. 2—

45-year-old woman with history of right breast fibroepithelial lesion. A, Contrast-enhanced digital mammography shows mass (arrows) in upper outer left breast on mediolateral oblique (MLO) (left) and craniocaudal (CC) (right) low-energy images. B, Associated mass enhancement (arrows) is present on MLO (left) and CC (right) iodine images. C and D, Gray-scale (C) and color Doppler (D) ultrasound images of left breast show correlative oval circumscribed parallel homogeneously hypoechoic mass at 2-o’clock position, 8 cm from nipple. Ultrasound-guided biopsy yielded benign phyllodes tumor, which was confirmed at surgical excision.

Fig. 3—

70-year-old woman with history of left breast atypical ductal hyperplasia. A, Contrast-enhanced digital mammography shows focal nonmass enhancement (arrows) at postsurgical scar site on craniocaudal (left) and mediolateral oblique (right) iodine images. No correlate was identified on low-energy images or ultrasound evaluation. B, Sagittal subtraction T1-weighted postcontrast MR image shows oval enhancing mass (arrow) that correlates with finding on iodine images (A). MRI-guided biopsy yielded invasive lobular carcinoma.

Fig. 4—

42-year-old woman with history of lumpectomy for right breast ductal carcinoma in situ. A, Contrast-enhanced digital mammography of right breast upper outer quadrant shows grouped amorphous calcifications (arrows) separate from postsurgical scar site on low-energy (magnification, insets) craniocaudal (CC) (left) and mediolateral (right) images. B, Iodine images show associated enhancement (arrows) on CC (left) and mediolateral oblique (right) views. Stereotactic biopsy of calcifications yielded ductal carcinoma in situ.