Résumé
Objective: to evaluate positive predictive values of imaging features to differentiate benign from malignant non-mass enhancing (NME) lesions on breast MRI through a 5-year follow-up. Materials and methods: we conducted a retrospective single-center cross-sectional study at Montpellier University Hospital, reviewing 208 MR examinations with NME lesions from January 2017 to December 2018. A total of 167 NME lesions in 153 patients were included. MRI features were assessed using the BI-RADS 5th edition lexicon, and clinical data were collected from electronic medical records. Reference standard was histopathology when available, or a 5-year follow-up otherwise. Results: of the 167 NME lesions, 135 (81%) were benign and 32 (19%) were malignant. Significant differences were observed between benign and malignant lesions in distribution patterns as well as internal enhancement patterns. Segmental distribution and clumped enhancement patterns showed a PPV for malignancy of 46.7% and 57.1% respectively. The association of a segmental distribution and a clumped pattern reached the highest PPV for malignancy (85.7%). Homogeneous linear NME smaller than 1cm, as well as triangular shaped or thick linear NME located at the edge of the gland both showed a PPV for cancer of 0% in our cohort. Besides, NME described in a context of cancer staging had a PPV of 52.6%, regardless of the side or the features of the lesion. Conclusion: we confirmed that a segmental distribution and a clumped pattern of enhancement are strong indicators of malignancy in NME lesions, and that their combination further increases malignancy likelihood. Conversely, as previously suggested, small homogeneous linear NME <1cm and thick NME at the edge of the gland could be categorized BI-RADS 3 and managed with follow-up. In a context of cancer staging, there are no criteria sufficiently relevant to avoid biopsy.