A ccording to the Breast Imaging-Reporting and Data System (BI-RADS), non-mass enhancement (NME) on magnetic resonance imaging (MRI) is defined as an enhanced area, not meeting the criteria for a mass, such as having nonconvex borders, intervening fat, or fibroglandular tissue between the enhancing components. 1 NME should be described using the BI-RADS lexicon regarding distribution (focal, linear, segmental, regional, multiple regions, and diffuse) and internal enhancement patterns (homogenous, heterogeneous, clumped, and clustered ring). A broad range of disease entities from benign to malignant lesions, such as intraductal papilloma, atypical ductal hyperplasia, apocrine metaplasia, radial scar, complex sclerosing lesions, ductal carcinoma in situ (DCIS), and invasive carcinoma, can present as NME. 2 Preoperative MRI of the breast is still widely used for staging patients with newly diagnosed breast cancer. Conducting MRI as part of the preoperative evaluation in these patients considering breast conservation surgery can potentially reduce the local recurrence rate. Owing to its high sensitivity for detecting breast cancers, preoperative breast MRI leads to conversion from wide local excision to more extensive surgery in 11.3%-12.8% of patients. However, in 6.3%-6.6% of patients, this conversion occurs due to false-positive findings. 3,4 Baltzer et al investigated 151 biopsy-proven lesions suspicious on breast MRI and reported that NME was a major cause of false-positive breast MRI interpretations. 5 Other studies reported that preoperative MRI features associated with positive resection margins and more extensive surgery accompanied the presence of NME in tissues adjacent to the index cancer 6 and was associated with intraductal extension of the invasive cancer. These findings indicate that accurate diagnosis of additional NME on preoperative MRI is important in successful surgical treatment.However, unlike masses, the diagnostic accuracy of NME is lesser known. Among the BI-RADS lexicon, linear, segmental, clumped, clustered ring, and heterogeneous are