title: Characteristics of probably benign breast MRI lesions.
abstract: OBJECTIVE
  The purpose of our study was to describe the characteristics of probably benign breast MRI lesions and determine how these characteristics could be used to define the MRI BI-RADS 3 category.
  
  
  METHODS
  We prospectively collected morphology and kinetic data on lesions assessed as BI-RADS 3 in 2,569 consecutive breast MRI examinations from January 2003 through November 2006. The clinical indications for MRI, follow-up assessments, and pathology findings through May 2008 were collected from clinical records. Data were linked to the regional tumor registry to identify cases of malignancy in patients who did not follow-up at our institution. Frequency of BI-RADS 3 and cancer yield were calculated. Characteristics of probably benign lesions were analyzed for predictors of malignancy.
  
  
  RESULTS
  Three hundred sixty-two lesions were assessed as BI-RADS 3 in 260 (10.1%) of 2,569 examinations in 236 patients. The 362 lesions included 168 (46%) foci, 132 (36%) nonmasslike enhancements, and 62 (17%) masses. Delayed kinetic information was available in 275 lesions. The most suspicious delayed kinetic enhancement was persistent in 164 (60%) of 275, plateau in 47 (17%) of 275, and washout in 64 (23%) of 275. The cancer yield in patients with a BI-RADS 3 assessment was two (0.85%) of 236; both were ductal carcinoma in situ lesions. There were no malignancies in the 69 foci with 100% persistent enhancement.
  
  
  CONCLUSIONS
  The characteristics of BI-RADS 3 lesions were highly variable in our population, and the risk of malignancy was low (0.85%). Assigning foci with 100% persistent enhancement to the BI-RADS 2 category can decrease the frequency of BI-RADS 3 assessment and maintain a likelihood of malignancy in less than 2% of cases.
authors.affiliation: Department of Radiology, University of Washington Medical Center, Seattle, WA, USA. preby@u.washington.edu
authors.forename: Peter R
authors.initials: PR
authors.lastname: Eby
authors.forename: Wendy B
authors.initials: WB
authors.lastname: DeMartini
authors.forename: Robert L
authors.initials: RL
authors.lastname: Gutierrez
authors.forename: Monica H
authors.initials: MH
authors.lastname: Saini
authors.forename: Sue
authors.initials: S
authors.lastname: Peacock
authors.forename: Constance D
authors.initials: CD
authors.lastname: Lehman
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001941:Breast Diseases / Q000175:diagnosis*; D001943:Breast Neoplasms / Q000175:diagnosis; D003287:Contrast Media / Q000493:pharmacokinetics; D003937:Diagnosis, Differential; D005260:Female; D019786:Gadolinium DTPA / Q000493:pharmacokinetics; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008875:Middle Aged; D011446:Prospective Studies; D012042:Registries; D012189:Retrospective Studies
chemical_list: D003287:Contrast Media; C064925:gadodiamide; D019786:Gadolinium DTPA