title: Breast Magnetic Resonance Imaging for Assessment of Internal Mammary Lymph Node Status in Breast Cancer.
abstract: OBJECTIVE
  The purpose of this study was to assess magnetic resonance imaging (MRI) features of malignant internal mammary lymph nodes (IMLNs) and benign IMLNs in breast cancer patients.
  
  
  METHODS
  From 2009 to 2014, the records of 85 patients with IMLNs were archived using MRI report data; 26 patients with small size (long axis diameter <5 mm) nodes were subsequently excluded. The current study evaluated internal mammary lymph nodes in 59 patients who underwent breast MRI for breast cancer staging and for posttherapy follow-up. All MRI findings were retrospectively evaluated. Malignancy was determined based on pathologic examination and positron emission tomography computed tomography findings. Independent t-tests, Mann-Whitney U tests, chi-square tests, and receiver operating characteristics (ROC) curve analysis were used.
  
  
  RESULTS
  Among MRI features, there were statistically significant differences between benign and malignant IMLN groups, in short axis length (3.6±1.3 vs. 8.2±2.9 mm, respectively), long axis length (8.1±2.4 vs. 14.5±4.8 mm, respectively), short/long axis ratio (0.45±0.10 vs. 0.59±0.17, respectively), absent fatty hilum (mean, 0% vs. 95%, respectively), and restricted diffusion (15.8% vs. 85.0%, respectively) (p<0.050). Multiplicity and location of intercostal spaces was not different between the two groups. Short axis length was the most discriminative variable for predicting metastatic nodes (area under the ROC curve, 0.951; threshold, 4 mm; sensitivity, 92.5%; specificity, 84.2%).
  
  
  CONCLUSIONS
  Conventional MRI and diffusion-weighted MRI are helpful to detect metastasis of internal mammary lymph nodes in breast cancer.
authors.affiliation: Division of Radiology, Seoul St. Mary's Hospital, The Catholic University of Korea College of Medicine, Seoul, Korea.
authors.forename: Hyung Won
authors.initials: HW
authors.lastname: Lee
authors.affiliation: Division of Radiology, Seoul St. Mary's Hospital, The Catholic University of Korea College of Medicine, Seoul, Korea.
authors.forename: Sung Hun
authors.initials: SH
authors.lastname: Kim
keywords: Breast neoplasms; Lymph nodes; Magnetic resonance imaging; Neoplasm metastasis