title: A pilot study to determine the diagnostic criteria of spiculated masses for BI-RADS MRI category 5: when to perform re-biopsy after discordant pathologic result?
abstract: BACKGROUND
  This study aimed to investigate (1) the MRI and clinical findings useful to differentiate malignant from benign spiculated masses and (2) the diagnostic criteria of spiculated masses for BI-RADS MRI category 5, for which any non-malignant biopsy result is considered discordant and a re-biopsy is recommended.
  
  
  METHODS
  Spiculated breast masses, depicted by 3.0/1.5-T contrast-enhanced MRI between June 2008 and March 2014, were retrospectively analyzed. Patient's age, lesion size, minimum/average apparent diffusion coefficient values (ADCmin/ADCave), and BI-RADS descriptors were compared between malignant and benign lesions. Based on these results, we assessed criteria to define category 5 spiculated masses with a ≥95 % probability of malignancy and evaluated their diagnostic performance.
  
  
  RESULTS
  A total of 140 lesions (Malignant group, n = 131; Benign group, n = 9) were analyzed. Patient's age, lesion size, ADCmin and ADCave showed significant differences between the two groups, while none of the BI-RADS descriptors, including kinetic curve assessment, showed any significant difference in frequency. Multivariate logistic regression analysis demonstrated that patient's age and lesion size were the significant predictive factors of malignancy. Of all the assessed criteria for category 5 spiculated masses, "age >50 years or size >9 mm, or both" were selected as the best criteria to minimize the possibility of unnecessary re-biopsies and inappropriate follow-up for malignancies.
  
  
  CONCLUSIONS
  Patient's age and lesion size are useful to differentiate malignant from benign spiculated breast masses. In cases with non-malignant biopsy results, spiculated masses with "age >50 years or size >9 mm, or both" are more likely malignant.
authors.affiliation: Department of Diagnostic Imaging and Nuclear Medicine, Kyoto University Graduate School of Medicine, 54 Shogoin-Kawaharacho Sakyo-ku, Kyoto, 606-8507, Japan. natsucom@kuhp.kyoto-u.ac.jp.
authors.forename: Natsuko
authors.initials: N
authors.lastname: Onishi
authors.affiliation: Department of Diagnostic Imaging and Nuclear Medicine, Kyoto University Graduate School of Medicine, 54 Shogoin-Kawaharacho Sakyo-ku, Kyoto, 606-8507, Japan.
authors.forename: Masako
authors.initials: M
authors.lastname: Kataoka
authors.affiliation: Department of Diagnostic Imaging and Nuclear Medicine, Kyoto University Graduate School of Medicine, 54 Shogoin-Kawaharacho Sakyo-ku, Kyoto, 606-8507, Japan.
authors.forename: Shotaro
authors.initials: S
authors.lastname: Kanao
authors.affiliation: Department of Diagnostic Imaging and Nuclear Medicine, Kyoto University Graduate School of Medicine, 54 Shogoin-Kawaharacho Sakyo-ku, Kyoto, 606-8507, Japan.
authors.forename: Makiko
authors.initials: M
authors.lastname: Kawai
authors.affiliation: Department of Diagnostic Imaging and Nuclear Medicine, Kyoto University Graduate School of Medicine, 54 Shogoin-Kawaharacho Sakyo-ku, Kyoto, 606-8507, Japan.
authors.forename: Mami
authors.initials: M
authors.lastname: Iima
authors.affiliation: Department of Diagnostic Imaging and Nuclear Medicine, Kyoto University Graduate School of Medicine, 54 Shogoin-Kawaharacho Sakyo-ku, Kyoto, 606-8507, Japan.
authors.forename: Akane
authors.initials: A
authors.lastname: Ohashi
authors.affiliation: Department of Breast Surgery, Kyoto University Graduate School of Medicine, 54 Shogoin-Kawaharacho Sakyo-ku, Kyoto, 606-8507, Japan.
authors.forename: Masakazu
authors.initials: M
authors.lastname: Toi
authors.affiliation: Department of Diagnostic Imaging and Nuclear Medicine, Kyoto University Graduate School of Medicine, 54 Shogoin-Kawaharacho Sakyo-ku, Kyoto, 606-8507, Japan.
authors.forename: Kaori
authors.initials: K
authors.lastname: Togashi
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D001706:Biopsy / Q000379:methods; D001943:Breast Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology*; D003287:Contrast Media; D005260:Female; D006801:Humans; D016015:Logistic Models; D008279:Magnetic Resonance Imaging / Q000379:methods; D008875:Middle Aged; D010865:Pilot Projects; D055815:Young Adult
chemical_list: D003287:Contrast Media
keywords: BI-RADS; Breast MRI; Breast cancer; Radial scar; Spiculated mass