Preoperative Evaluation of Non-Mass-Like Enhancement on Magnetic Resonance Imaging for Measuring Tumor Extent and Affecting Surgical Margin Status in Breast Cancer Patients

Purpose: This study investigated the correlation between non-mass-like enhancement (NME) observed on preoperative breast magnetic resonance imaging (MRI) and the actual pathological size of breast cancer. We further examined the effect of NME on the positive resection margins during partial mastectomy.Methods: We retrospectively collected data from breast cancer patients who underwent surgery between January 2018 and September 2020. Patients were divided into two groups based on their MRI findings: NME and no-NME (mass-like lesion only) groups. The medical records, including MRI findings and clinicopathological information of patients, were collected retrospectively, and correlations with pathologic results were analyzed. Propensity score matching was applied to develop comparable cohorts of the NME group and no-NME group.Results: This study included a total of 317 patients, with 66 and 251 patients in the NME and no-NME groups, respectively. The mean pathologic size of invasive lesion was significantly smaller than the mean lesion size in the NME group (1.55±1.39 cm vs. 3.45±1.81 cm, p<0.001). The mean pathologic size of ductal carcinoma in situ (DCIS) lesions was larger than that in the NME group but without statistical significance (3.91±2.67 cm vs. 3.50±1.79 cm, p=0.326). In the NME group, NME estimated DCIS size to within 1 cm in 20 patients (30.3%) and overestimated invasive lesion size by more than 1 cm in 31 patients (46.9%). NME (vs. no-NME; odds ratio [OR], 2.967; 95% confidence interval [CI], 0.878-10.025) showed a tendency to predict positive resection margins, but this was not statistically significant (p=0.080).Conclusion: NME findings on MRI showed a similar extent of DCIS lesions. NME findings on preoperative MRI should be considered an important factor for measuring the extent of tumors, especially in DCIS patients.