Radiologic-Pathologic Correlation of Nonmass Enhancement Contiguous with Malignant Index Breast Cancer Masses at Preoperative Breast MRI.

Purpose To determine the pathologic features of nonmass enhancement (NME) directly adjacent to biopsy-proven malignant masses (index masses) at preoperative MRI and determine imaging characteristics that are associated with a malignant pathologic condition. Materials and Methods This retrospective study involved the review of breast MRI and mammography examinations performed for evaluating disease extent in patients newly diagnosed with breast cancer from July 1, 2016, to September 30, 2019. Inclusion criteria were limited to patients with an index mass and the presence of NME extending directly from the mass margins. Wilcoxon rank sum test, Fisher exact test, and χ test were used to analyze cancer, patient, and imaging characteristics associated with the NME diagnosis. Results Fifty-eight patients (mean age, 58 years ± 12 [SD]; all women) were included. Malignant pathologic findings for mass-associated NME occurred in 64% (37 of 58) of patients, 43% (16 of 37) with ductal carcinoma in situ and 57% (21 of 37) with invasive carcinoma. NME was more likely to be malignant when associated with an index cancer that had a low Ki-67 index (<20%) ( = .04). The presence of calcifications at mammography correlating with mass-associated NME was not significantly associated with malignant pathologic conditions ( = .19). The span of suspicious enhancement measured at MRI overestimated the true span of disease at histologic evaluation ( < .001), while there was no evidence of a difference between span of calcifications at mammography and true span of disease at histologic evaluation ( = .27). Conclusion Mass-associated NME at preoperative MRI was malignant in most patients with newly diagnosed breast cancer. The span of suspicious enhancement measured at MRI overestimated the true span of disease found at histologic evaluation. Breast, Mammography © RSNA, 2024 See also the commentary by Newell in this issue.