title: Nonmalignant breast lesions: ADCs of benign and high-risk subtypes assessed as false-positive at dynamic enhanced MR imaging.
abstract: OBJECTIVE
  To evaluate the diffusion-weighted (DW) imaging characteristics of nonmalignant lesion subtypes assessed as false-positive findings at conventional breast magnetic resonance (MR) imaging.
  
  
  METHODS
  This HIPAA-compliant retrospective study had institutional review board approval, and the need for informed patient consent was waived. Lesions assessed as Breast Imaging Reporting and Data System category 4 or 5 at clinical dynamic contrast material-enhanced MR imaging that subsequently proved nonmalignant at biopsy were retrospectively reviewed. One hundred seventy-five nonmalignant breast lesions in 165 women were evaluated. Apparent diffusion coefficients (ADCs) from DW imaging (b = 0, 600 sec/mm(2)) were calculated for each lesion and were compared between subtypes and with an ADC threshold of 1.81 × 10(-3) mm(2)/sec (determined in a prior study to achieve 100% sensitivity).
  
  
  RESULTS
  Eighty-one (46%) lesions exhibited ADCs greater than the predetermined threshold. The most prevalent lesion subtypes with mean ADCs above the threshold were fibroadenoma ([1.94 ± 0.38 {standard deviation}] × 10(-3) mm(2)/sec; n = 30), focal fibrosis ([1.84 ± 0.48] × 10(-3) mm(2)/sec; n = 19), normal tissue ([1.81 ± 0.47] × 10(-3) mm(2)/sec; n = 13), apocrine metaplasia ([2.01 ± 0.38] × 10(-3) mm(2)/sec; n = 13), usual ductal hyperplasia ([1.83 ± 0.49] × 10(-3) mm(2)/sec; n = 12), and inflammation ([1.95 ± 0.46] × 10(-3) mm(2)/sec; n = 10). Atypical ductal hyperplasia ([1.48 ± 0.36] × 10(-3) mm(2)/sec; n = 23) was the most common lesion subtype with ADC below the threshold. Lymph nodes exhibited the lowest mean ADC of all nonmalignant lesions ([1.28 ± 0.23] × 10(-3) mm(2)/sec; n = 4). High-risk lesions (atypical ductal hyperplasia and lobular neoplasia) showed significantly lower ADCs than other benign lesions (P < .0001) and were the most common lesions with ADCs below the threshold.
  
  
  CONCLUSIONS
  Assessing ADC along with dynamic contrast-enhanced MR imaging features may decrease the number of avoidable false-positive findings at breast MR imaging and reduce the number of preventable biopsies. The ability of DW imaging to help differentiate high-risk lesions requiring additional work-up from other nonmalignant subtypes may further improve patient care.
  
  
  BACKGROUND
  http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.12112672/-/DC1.
authors.affiliation: Departments of Radiology, University of Washington School of Medicine, Seattle Cancer Care Alliance, 825 Eastlake Ave E, G3-200, Seattle, WA 98109-1023, USA.
authors.forename: Sana
authors.initials: S
authors.lastname: Parsian
authors.forename: Habib
authors.initials: H
authors.lastname: Rahbar
authors.forename: Kimberly H
authors.initials: KH
authors.lastname: Allison
authors.forename: Wendy B
authors.initials: WB
authors.lastname: Demartini
authors.forename: Matthew L
authors.initials: ML
authors.lastname: Olson
authors.forename: Constance D
authors.initials: CD
authors.lastname: Lehman
authors.forename: Savannah C
authors.initials: SC
authors.lastname: Partridge
mesh_terms: D000328:Adult; D000368:Aged; D001706:Biopsy; D001941:Breast Diseases / Q000175:diagnosis* / Q000473:pathology; D001943:Breast Neoplasms / Q000175:diagnosis; D016009:Chi-Square Distribution; D003287:Contrast Media; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005189:False Positive Reactions; D005260:Female; D019786:Gadolinium DTPA; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008875:Middle Aged; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D018709:Statistics, Nonparametric
chemical_list: D003287:Contrast Media; C064925:gadodiamide; D019786:Gadolinium DTPA