title: Categorization of non-mass-like breast lesions detected by MRI.
abstract: BACKGROUND
  Breast MR imaging has emerged as a highly sensitive modality for the imaging of breast tumors. However, a standardized method of interpretation of lesions showing non-mass-like enhancement does not exist. The purpose of this study was to analyze the features of non-mass-like breast lesions detected by MRI, and to establish a standardized method of interpretation to allow categorization of these lesions.
  
  
  METHODS
  A retrospective review was performed for 102 consecutive nonpalpable mammographically occult, non-mass-like lesions detected by MRI that had undergone ultrasound-guided vacuum-assisted biopsy. MR imaging was performed on a 1.5-Tesla system. The distribution patterns were classified into three categories as follows: single quadrant/solitary lesion (linear), single quadrant/grouped lesion (focal, regional, segmental), and multiquadrant lesion (multiple regions, diffuse). The presence of a ductal pattern was assessed in the enhancing lesions after the tumor distribution had been decided. In addition to the BI-RADS-MRI descriptors, the presence of clustered ring enhancement was also assessed in heterogeneous enhancing lesions. We divided non-mass-like lesions into those with a small (category 3a), moderate (category 3b), or substantial (category 4) likelihood of malignancy.
  
  
  RESULTS
  The features with the highest positive predictive value (PPV) for cancer were clustered ring enhancement (67%) (P = 0.004), a branching-ductal pattern (38%) (P = 0.003), and clumped architecture (20%). The PPV for cancer of a linear-ductal pattern was 11% (1/9). All lesions showing multiquadrant distribution, linear-nonspecific lesion, non-branching pattern with homogeneous and stippled internal architectures, and heterogeneous lesion without clustered ring enhancement were diagnosed as benign.
  
  
  CONCLUSIONS
  Non-mass-like breast lesions detected on MRI showing a clustered ring enhancement, a branching-ductal pattern, and clumped architecture should be evaluated further by biopsy (category 4), while lesions not showing these characteristics may be observed without unnecessary intervention (category 3a). Lesions showing a linear-ductal pattern may be followed carefully or evaluated by biopsy as needed (category 3b).
authors.affiliation: Breast Center, Kameda Medical Center, 929 Higashi-cho, Kamogawa, Chiba 296-8602, Japan. n.sakamoto@kameda.jp
authors.forename: Naomi
authors.initials: N
authors.lastname: Sakamoto
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Tozaki
authors.forename: Kuniki
authors.initials: K
authors.lastname: Higa
authors.forename: Yuko
authors.initials: Y
authors.lastname: Tsunoda
authors.forename: Tomoko
authors.initials: T
authors.lastname: Ogawa
authors.forename: Satoko
authors.initials: S
authors.lastname: Abe
authors.forename: Shinji
authors.initials: S
authors.lastname: Ozaki
authors.forename: Masaaki
authors.initials: M
authors.lastname: Sakamoto
authors.forename: Tomoko
authors.initials: T
authors.lastname: Tsuruhara
authors.forename: Naoko
authors.initials: N
authors.lastname: Kawano
authors.forename: Takako
authors.initials: T
authors.lastname: Suzuki
authors.forename: Norie
authors.initials: N
authors.lastname: Yamashiro
authors.forename: Eisuke
authors.initials: E
authors.lastname: Fukuma
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001941:Breast Diseases / Q000145:classification / Q000175:diagnosis* / Q000401:mortality; D002285:Carcinoma, Intraductal, Noninfiltrating / Q000145:classification / Q000175:diagnosis* / Q000401:mortality; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008327:Mammography; D008875:Middle Aged; D011379:Prognosis; D012189:Retrospective Studies; D015996:Survival Rate