An accurate loco-regional staging and preoperative assessment of breast cancer are considered of key importance to guide treatment decisions [12]. MRI is a valuable technique and has been increasingly used particularly in cases in which sonomammography are inconclusive or yield discrepancies (Fig. 3). It may improve the analysis of the local extent of breast cancer [13], thus increasing the rates of complete resection and reducing the number of re-operations [14].
Therefore, in this study, we aimed to evaluate the performance of CE-MRI and qualitative DWI-MRI in preoperative loco-regional staging of malignant breast lesions as regards the local extension of the disease and axillary lymph node status, beyond standard assessment with mammography and ultrasound.
We divided our cases in this study into 2 groups: patients who underwent upfront surgery (37/50, 74%) and those who had received neoadjuvant chemotherapy before surgery (13/50, 26%).
We started the analysis of the upfront surgery group by correlating the size of the malignant lesion with the postoperative pathology results. CE-MRI showed the highest correlation while DWI showed the lowest (Fig. 4).
In a study performed by Gundry, tumor size was underestimated on both mammography and ultrasound (14 and 18 %, respectively); however, the size of the tumor at histology was not significantly different from that seen on MRI [15].
In our study, CE-MRI was able to detect the DCIS component of the malignant lesions in the form of area of non-mass enhancement giving better extent of the tumor size and consequently superior staging results over the sonomammography.
Kim et al. also stated that MRI was more accurate compared to mammography in the assessment of the DCIS size [16]. According to Hwang et al., MRI was superior to mammography in the detection of invasive components within DCIS [17].
Regarding lesion multiplicity in our study, the accuracy measures of CE-MRI were found to be higher than those of sonomammography with an overall accuracy of 83.78% for MRI and 67.57% for sonomammography with reference to the postoperative pathology results (Fig. 5). DWI-MRI was found to be unreliable due to its poor resolution in the detection of the small satellite lesions.
Additional lesions (multifocal or multicentric disease) have been shown in 31% of women with breast cancer. Even though mammography and ultrasonography can often detect the primary tumor, small additional lesions may be missed [15].
Selvi et al. stated that MRI is well known for its increased diagnostic value in detecting multifocal, multicentric, or contralateral disease unrecognized on conventional exams [18]. Moreover, the meta-analysis of 50 studies (10,811 women with breast cancer) performed by Lee et al. showed that MRI findings prompted conversion from lumpectomy to mastectomy in 12.8% of cases [4].
Appropriate evaluation of regional lymph node status (N) is important for staging, treatment planning, and prognosis [4]. In reference to the postoperative pathology results of axillary lymph nodes, the accuracy measures of sonomammography were found to be the highest among the imaging modalities, with an overall accuracy of 75.68% as compared to CE-MRI and DWI-MRI with the same accuracy of 72.97% (Figs. 5 and 6).
The reported axillary US sensitivities, and specificities are in the range of 45.2–100% and 50–89%, respectively, while those of DCE-MRI are 79–100% (relatively high) and 56–93% (relatively low), respectively, and 53.8–94.7% and 77–91.7%, respectively, of DW-MRI for ALN metastases [19].
In Chung et al. study, the sensitivity, specificity, and accuracy of axillary US and CE-MRI with DWI preoperatively were 100%, 83.3%, and 93.6%, respectively. Moreover, DW MRI showed superior diagnostic performance to axillary US [19] (Fig. 6).
According to Lee et al., high-resolution US is useful in the evaluation of lymph nodes at all levels while MRI can in addition detect internal mammary and supraclavicular adenopathy [4].
Kujis et al. also showed in a meta-analysis study done to demonstrate whether MRI can replace SLNB to exclude axillary lymph node metastasis, a false-negative rate of 8.61 % of the SLNB [20].
We then assessed the post-neoadjuvant group. We started the analysis of our cases by correlating the post-neoadjuvant therapy size of lesions with the postoperative pathology results. In our study, CE-MRI was found to be the best among the imaging modalities, with a p value of 0.013 (Fig. 7).
According to a study that included 160 patients who received neoadjuvant chemotherapy, the results showed that MRI correlated better with the size of the breast tumor remnants found in the assessment of the surgical specimen than did mammography and ultrasound [14]. Menzes et al. results suggest that DWI and ADC are useful for predicting tumor response to NAC in breast cancer patients [21].
Rosen et al. stated that the treatment options in the neoadjuvant setting depend on the amount of residual tumor. Palpation and conventional imaging (mammography and sonography) have been traditionally used, yet the tumor’s true size may be hindered by edema and necrosis at the tumor site [22].
Mammographic assessment becomes more difficult in denser breasts, with ill-defined tumors, or in areas of architectural distortion alone. Sonography may be more accurate with well-defined tumors but may still produce erroneous results [15].
MRI provides anatomic and physiologic evaluation of the tumor, so the findings are not influenced by necrosis and edema. And since the findings are based on the vascularity of the tumor, the effect of chemotherapy agents can be seen through inhibiting tumor angiogenesis [15]. However, some studies emphasize on the tendency of MRI to overestimate lesion size, particularly in women with invasive lobular carcinoma and DCIS [21].
Regarding post-neoadjuvant chemotherapy lymph nodes status in our study, sonomammography and DCE-MRI had the same statistical results, correlating with the postoperative pathology specimen results.
DCE-MRI is correlating better with the postoperative pathology specimen results regarding post-neoadjuvant chemotherapy lesions multiplicity.
MRI prior to NAC is essential especially if there is multicentric or diffuse disease. As a result of therapy, these lesions become less conspicuous with decreased contrast enhancement [15].
According to a study of 163 patients, preoperative MRI showed 91.04% sensitivity in detecting additional lesions either in the ipsilateral or contralateral breast [18].
Direct skin invasion and involvement of the nipple, pectoralis muscle, or chest wall should be mentioned in radiology reports because their presence changes surgical planning [4].
DCE-MRI and sonomammography correlated well with the postoperative pathology specimen regarding nipple affection while both overestimated the skin involvement. DWI-MRI was found to be unreliable in the estimation of both due to its poor resolution.
According to Gundry, breast MRI can determine chest wall invasion better than mammography or ultrasound. Tumor involvement of the chest wall, regardless of primary tumor size, changes the disease stage to IIIB [15].
We had few limitations in this study, the small number of patients we included, especially in the post-neoadjuvant group.