title: False-positive findings at contrast-enhanced breast MRI: a BI-RADS descriptor study.
abstract: OBJECTIVE
  Breast MRI has high sensitivity in breast cancer detection, and the BI-RADS MRI lexicon was a step toward standardized description of lesions. However, false-positive findings occur and lead to unnecessary biopsy. The purpose of this investigation was to identify criteria for false-positive findings in clinical practice.
  
  
  METHODS
  Eligible for investigation were all breast MRI examinations from a consecutive 16-month time period that had histopathologic verification and findings classified as BI-RADS category 4-6 in the initial MRI report. Accordingly, 132 patients with 120 malignant and 31 benign lesions were enrolled. Two blinded observers categorized lesions into mass or nonmass and used BI-RADS to identify descriptor distribution differences between the benign and malignant subgroups.
  
  
  RESULTS
  The ratio of mass to nonmass lesions differed significantly (p < 0.001) between benign (1.2:1) and malignant (7:1) findings. Seventeen mass and 14 nonmass lesions were false-positive, and 105 mass and 15 nonmass lesions were true-positive. Among mass lesions, it was possible to differentiate malignant and benign lesions on the basis of margin (smooth, irregular, or spiculated) and dynamic enhancement features (p < 0.05). Among nonmass lesions, only stippled enhancement had a significant difference between the subgroups (p < 0.05). Tumor diameter had no influence on the correct diagnosis of nonmass lesions (p = 0.301). Conversely, among mass lesions, false-positive lesions were smaller than true-positive lesions (p = 0.01).
  
  
  CONCLUSIONS
  Nonmass lesions were the major cause of false-positive breast MRI findings. BI-RADS descriptors are not sufficient for differentiating benign and malignant nonmass lesions.
authors.affiliation: Institute of Diagnostic and Interventional Radiology, Friedrich-Schiller-University Jena, D-07740 Jena, Germany. pascal.baltzer@med.uni-jena.de
authors.forename: Pascal A T
authors.initials: PA
authors.lastname: Baltzer
authors.forename: Matthias
authors.initials: M
authors.lastname: Benndorf
authors.forename: Matthias
authors.initials: M
authors.lastname: Dietzel
authors.forename: Mieczyslaw
authors.initials: M
authors.lastname: Gajda
authors.forename: Ingo B
authors.initials: IB
authors.lastname: Runnebaum
authors.forename: Werner A
authors.initials: WA
authors.lastname: Kaiser
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001706:Biopsy; D001943:Breast Neoplasms / Q000175:diagnosis* / Q000473:pathology; D016009:Chi-Square Distribution; D003287:Contrast Media; D005189:False Positive Reactions; D005260:Female; D019786:Gadolinium DTPA; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D016013:Likelihood Functions; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008875:Middle Aged; D012680:Sensitivity and Specificity; D018709:Statistics, Nonparametric; D013382:Subtraction Technique
chemical_list: D003287:Contrast Media; D019786:Gadolinium DTPA