Radiologic-Pathologic Correlation of Non-Mass Enhancement Associated with Malignant Breast Cancer Masses

Abstract Objective: To determine pathologic correlation of NME associated directly with malignant index masses on preoperative MRI and determine imaging characteristic predictors of malignant outcomes to inform surgical management. Methods: This retrospective study reviewed breast MRI examinations performed for extent of disease in newly diagnosed breast cancer patients from 7/1/16 to 9/30/19. Inclusion criteria were limited to patients with a malignant index mass and the presence of NME extending from the mass margins. Fisher’s exact test and Chi-square test were used to analyze cancer, patient, and imaging characteristics associated with the NME diagnosis and determine predictors of malignant outcomes. Results: This study included 58 patients (mean age 58 ± 12 years). Malignant outcomes for mass-associated NME occurred in 63.8% (37/58) of cases: 43.2% (16/37) in situ and 56.8% (21/37) invasive carcinoma. Longer span of mass-associated NME and lower Ki-67 index were significant predictors of malignant mass-associated NME (p<0.05). The presence of calcifications correlating with mass-associated NME was not a significant predictor of malignant outcomes (p=0.19). Span of disease measured on MRI overestimates the true span of disease on histologic evaluation (p<0.01). There was no significant difference in span of disease measured on mammography when correlating calcifications were present and true span of disease on histologic evaluation (p=0.27). Conclusion: The majority of mass-associated NME on preoperative MRI is malignant (63.8%). Longer span of mass-associated NME and lower Ki-67 index were significantly associated with malignant outcomes. However, total span of disease measured on MRI tends to overestimate the true histologic span of disease.