title: Frequency of Malignancy and Imaging Characteristics of Probably Benign Lesions Seen at Breast MRI.
abstract: OBJECTIVE
  The purposes of this study were to evaluate the frequency, follow-up compliance, and cancer rate of MRI BI-RADS category 3 lesions and to determine the cancer rate for individual BI-RADS descriptors.
  
  
  METHODS
  A retrospective review was conducted of breast MRI examinations with an assessment of probably benign (BI-RADS category 3) from among 4279 consecutive breast MRI examinations performed from January 2005 through December 2009. The review revealed 282 (6.6%) examinations with 332 lesions defined as BI-RADS 3. Pathologic results, 2 years of follow-up imaging findings, or both were reviewed. The frequency of BI-RADS 3 assessments, follow-up imaging compliance, and cancer yield were calculated. Three fellowship-trained breast imagers reevaluated all lesions and recorded descriptors from the MRI lexicon of the fifth edition of the BI-RADS atlas. The distribution and likelihood of malignancy for each descriptor were calculated.
  
  
  RESULTS
  The follow-up compliance rate was 84.3% (280/332), and the malignancy rate was 4.3% (12/280). There were 50 (17.9%) individual foci, 61 (21.8%) multiple foci, 74 (26.4%) masses, and 95 (33.9%) nonmass enhancement lesions. Masses were most commonly oval (59.5% [44/74]), circumscribed (75.7% [56/74]), and homogeneously enhancing (43.2% [32/74]). Nonmass enhancement was most commonly focal (57.9% [55/95]) with heterogeneous enhancement (53.7% [51/95]) Most of the lesions had persistent kinetics (74.3% [208/280]). The background parenchymal enhancement was most commonly mild (51.1% [143/280]).
  
  
  CONCLUSIONS
  MRI BI-RADS category 3 is not frequently used, and the levels of patient compliance with follow-up imaging are acceptable. The cancer yield for probably benign lesions is greater for MRI-detected than for mammographically detected lesions, especially for specific BI-RADS descriptors.
authors.affiliation: 1 Department of Radiology, Duke University Medical Center, Box 3808, Durham, NC 27710.
authors.forename: Lars J
authors.initials: LJ
authors.lastname: Grimm
authors.affiliation: 1 Department of Radiology, Duke University Medical Center, Box 3808, Durham, NC 27710.
authors.forename: Andy L
authors.initials: AL
authors.lastname: Anderson
authors.affiliation: 1 Department of Radiology, Duke University Medical Center, Box 3808, Durham, NC 27710.
authors.forename: Jay A
authors.initials: JA
authors.lastname: Baker
authors.affiliation: 1 Department of Radiology, Duke University Medical Center, Box 3808, Durham, NC 27710.
authors.forename: Karen S
authors.initials: KS
authors.lastname: Johnson
authors.affiliation: 1 Department of Radiology, Duke University Medical Center, Box 3808, Durham, NC 27710.
authors.forename: Ruth
authors.initials: R
authors.lastname: Walsh
authors.affiliation: 1 Department of Radiology, Duke University Medical Center, Box 3808, Durham, NC 27710.
authors.forename: Sora C
authors.initials: SC
authors.lastname: Yoon
authors.affiliation: 1 Department of Radiology, Duke University Medical Center, Box 3808, Durham, NC 27710.
authors.forename: Sujata V
authors.initials: SV
authors.lastname: Ghate
mesh_terms: D001943:Breast Neoplasms / Q000175:diagnosis* / Q000453:epidemiology; D003266:Continuity of Patient Care; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008875:Middle Aged; D010349:Patient Compliance; D012189:Retrospective Studies
keywords: BI-RADS; MRI; breast cancer; probably benign