The study aimed to evaluate diagnostic accuracy of CEDM for characterization of focal asymmetries in 2D mammography. Few studies evaluated this topic and most of them have investigated asymmetry in general [3, 7, 8]. However, this study focused exclusively on focal asymmetry. The overall results of our study confirmed the higher diagnostic accuracy of CEDM with second-look US than sonomammography only.
MRI lexicon for morphological analysis according to ACR 2018 classifies the lesions in subtracted images into focus, mass, and non-mass enhancement . Our results showed a positive moderate correlation between lesions in CEDM and pathology (0.6) as majority of malignant pathology was detected as mass enhancement particularly and benign pathology and normality in non-enhanced lesions. A recent study documented a significant correlation between asymmetry showing “mass or non-mass enhancement” and malignancy and between non-enhancing findings and benign pathology . CEDM has the potential to depict angiogenesis, which is more pronounced in IDC [13, 14]. As in our study, most of moderate or intense enhanced lesions were IDC.
As regard mass enhancement descriptors, the highest incidence of malignant lesions was correlated to irregular margin followed by irregular shape then intensity of enhancement and finally pattern of enhancement. A smooth circumscribed margin is seen in benign lesions versus a speculated or irregular margin seen in malignancy; heterogeneous enhancement pattern was exhibited mostly by malignant lesions. Dark septa are seen in fibroadenomas, which agree with other documentations [12, 15, 16]. Mass with rim enhancement is an unreliable sign in predicting malignancy. Ultrasound assessment of wall nodularity and thickness is vital [12, 15, 16]. In our finding about rim enhancement, one case was IDC and 4 cases were benign, namely, 3 abscesses cases and 1 granulomatous mastitis.
As regard non-mass enhancement descriptors in our study, suspicious heterogeneous pattern with segmental and regional distributions showed benign pathology and a single case of unilateral multiregional enhancement was malignant by pathology. In contrast to other literatures noticed the strong correlation between ductal/linear, segmental, focal distributions and heterogonous and clumped patterns with malignant pathology but regional, bilateral multiregional, and diffuse distribution were related to benignity [6, 12, 17]. Assessment of non-mass morphological descriptors is more subjective and gives more false-positive results .
Moreover, weak or absent enhancement characterizes benign lesions which agrees with our study as 4 cases of faint enhancement were benign lesions and all 5 non-enhancing lesions were benign lesions or representing normal parenchymal enhancement .
Invasive ductal carcinoma was described in a recent study as an intensely enhancing mass with speculated and irregular margins in majority of enhancing masses and much less presented as non-mass enhancement or non-enhancement and displayed no ring enhancement which partially agrees with our study as IDC presented as an intense or moderate enhancing mass with speculated and irregular margins in 95% of cases and as non-mass enhancement in 25% of cases, but rim enhancement was noticed in only one case of IDC .
The study showed that the case of faintly enhanced multiple foci was abscess which agrees with a recent study revealed that the intense enhancement is the discriminating element in focus enhancement. Some studies reported that the faint bilateral foci could be considered as normal background parenchymal enhancement (BPE) after low energy images review and second look US [6, 7, 16].
Microcalcifications with enhancement are favorable to malignant diagnosis, however, lack of enhancement may be diagnostic for non-malignant lesions or noninvasive subgroup cancers [4, 17]. Amorphous or pleomorphic calcifications +/− mass on mammograms have high cancer prediction rate of DCIS lesions showing weak enhancement . Previous studies are comparable to our study, which showed 12 cases of calcifications with mammographic focal asymmetry. Nine cases of suspicious calcifications showed intense and moderate enhancing mass (IDC).
When compared to sonomammography, CEDM showed higher sensitivity (77.8% vs. 65.7), NPV (60% vs. 20%), and accuracy (0.6 vs. 0.2), yet lower specificity (81.8% vs. 100%) and PPV (91.3% vs 100%). Our study agrees with another study comparing CEDM to digital mammography in terms of sensitivity (90.6% vs. 83.11%) and NPV (0.8 vs. 0.6), while disagrees in terms of specificity (97.7% vs. 60.4%) and PPV (98.5 vs. 79) (14). In our study, the higher sensitivity of CEDM reflected the higher value in diagnosis of true malignant cases, while higher specificity of sonomammography reflected higher ability in detection of true benign cases. However, specificity of CEDM in our study was less than sonomammography, but it is still acceptable and could be easily improved. PPV of sonomammography reflected the prominent malignant features by sonomammography more than CEDM and better chance for malignancy detection by combination of the 2 modalities. NPV of CEDM was much higher reflecting its higher value in diagnosis of negative or benign cases and avoidance of unnecessary biopsies.
No false-positive cases were detected by sonomammography but only 2 in CEDM (abscess and fibroadenoma), which could be improved by more working up on this new modality and more experience of readers. False-negative cases by CEDM were much less, reflecting overestimation of the focal asymmetry by sonomammography. CEDM has higher accuracy when compared to sonomammography (0.6 and 0.2 respectively) reflecting its higher reliability.
CEDM can detect multiple and bilateral lesions and it is recommended in high-risk patients [18, 19]. The detection rate of multiplicity was higher in CEDM than sonomammography.
Some limitations were found in our study such as subjective assessment of the degree of enhancement on CEDM, the small number of patients in particular subgroups, as microcalcifications (8 cases) or in situ cancers (1 case), in addition to manual injection of contrast which hindered kinetic assessment of the lesions.