Background Non-mass enhancements (NME) with invasive components account for 10-42% of total malignant NMEs. The factors associated with invasiveness on magnetic resonance imaging (MRI) could be useful for clinical assessment and treatment. Purpose To evaluate the clinical significances of the distributions and internal enhancement patterns (IEP) of malignant NMEs on 3-T breast MRI. Material and Methods A total of 448 consecutive women with newly diagnosed breast cancer that had undergone preoperative MRI and surgery between February 2013 and March 2016 were identified. After exclusions, 72 malignant NMEs without a mass in 72 women (mean age = 51.5 years) were included. Two readers independently assessed distributions and IEPs of NME, according to the Breast Imaging Reporting and Data System lexicon fifth edition. Collected data included the presence of invasion and histopathologic factors. Results A clustered ring IEP was significantly associated with invasive cancer (75.0%, P = 0.001, Reader1; 72.9%, P < 0.001, Reader 2), absence of necrosis (79.0%, P < 0.001; 72.1%, P < 0.001, respectively), and high Ki-67 expression (74.2%, P = 0.048; 74.2%, P = 0.003, respectively). A clumped IEP was related to ductal carcinoma in situ (33.3%, P = 0.025; 50.0%, P = 0.001, respectively), absence of lymph node metastasis (24.1%, P = 0.029; 31.5%, P = 0.030, respectively), and presence of necrosis (34.5%, P = 0.003; 44.8%, P = 0.001, respectively). Conclusion The presence of a clustered ring IEP in patients with breast cancer was found to be significantly associated with invasive breast cancer and high Ki-67 expression.
Keywords: Breast cancer; Ki-67 expression; invasiveness; magnetic resonance imaging (MRI); non-mass enhancement (NME).