Tehran University of Medical Sciences Basic & Clinical Cancer Research 2228-6527 15 1 2024 01 07 1 8 Nasrin Ahmadinejad Advanced Diagnostic and Interventional Radiology Research Center (ADIR), Medical Imaging Center, Tehran University of Medical Sciences, Tehran, Iran Mohammad Hossein Golezar Student Research Committee, Faculty of Medicine, Shahed University, Tehran, Iran Maedeh Rouzbahani School of Medicine, Tehran University of Medical Sciences, Tehran, Iran Sara Hassanzadeh School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran Mohsen Rastkar Students’ Scientific Research Center, Tehran University of Medical Sciences, Tehran, Iran 2023 08 29 2023 10 09 Aim: The purpose of this study is to conduct a systematic review of the current knowledge regarding the diagnostic performance of MRI in the investigation of non-mass lesions of the breast. Method: Up to July 2022, PubMed, Scopus, Web of Science, and Embase were searched comprehensively. All studies examining the diagnostic performance of MRI in non-mass lesions were included except review articles, articles published in a language other than English, and case reports or series of cases. A literature review and data extraction were performed by two independent reviewers. A checklist for cross-sectional studies developed by the Joanna Briggs Institute (JBI) was used to assess sources of bias. Results: The systematic review included two studies. If any enhancement is present on MRI, most ultrasound NMLs will exhibit a non-mass-enhancement. We found that the distribution of non-mass enhancement lesions was primarily segmental and regional. The highest number of malignancies is associated with segmental distributions, since 81.8% of the cases with segmental enhancement were ductal carcinomas, specifically DCIS. Conclusion: Non-mass lesions of the US that do not enhance in MRI have a good prognosis. Breast cancer is very unlikely in these cases, so follow-up is acceptable unless there is a suspicion of malignancy on mammography. In cases where regional and segmental enhancement of NMLs occurs on CE-MRI, ductal carcinomas may be present, and a pathological examination is warranted. https://bccr.tums.ac.ir/index.php/bccrj/article/view/494