title: Apparent diffusion coefficient in differentiation between malignant and benign breast masses: does size matter?
abstract: OBJECTIVE
  To determine whether lesion size affects the diagnostic performance of apparent diffusion coefficient (ADC) in the evaluation of breast masses.
  
  
  METHODS
  Consecutive breast lesions detected at magnetic resonance imaging (MRI) from June 2010 to July 2013 were retrospectively reviewed. Differences in the ADCs of benign and malignant mass lesions were compared. Receiver operating characteristics analysis was performed to evaluate diagnostic performance of ADC regarding lesion size (≤ 1 cm or >1 cm) and their T2W signal intensities.
  
  
  RESULTS
  Seventy-four malignant lesions (77.9%) and 21 (22.1%) benign lesions were included. Twenty-two of the 95 (23.2%) masses measured ≤ 1 cm (mean 0.73 ± 0.4; range 0.51-0.8 cm) and 73/95 (76.9%) masses measured >1 cm (mean 2.11 ± 0.1; range 1.1-3.3 cm). The mean ADC was significantly lower for malignant than for benign lesions (mean for malignant lesion, 0.89 ± 0.29 × 10(-3) mm(2)/s; mean for benign lesions, 1.27 ± 0.42 × 10(-3) mm(2)/s; p<0.01). The optimal ADC cut-off for differentiating benign and malignant lesion was 1.088 × 10(-3) mm(2)/s with a sensitivity of 85.9% and specificity of 77% for lesions >1 cm. The sensitivity and specificity were lowered to 60% and 50%, respectively, for lesions of size ≤ 1. Maximal sensitivity and specificity were reached when the ADC value was used to evaluate T2-dark lesions.
  
  
  CONCLUSIONS
  Diffusion-weighted MRI is useful for characterizing masses that are hypointense on T2-weighted images. Lower sensitivity and specificity were found for breast lesions ≤ 1 cm.
authors.affiliation: Department of Radiology, Tuen Mun Hospital, Tuen Mun, Hong Kong. Electronic address: catherinewanws@gmail.com.
authors.forename: C W S
authors.initials: CW
authors.lastname: Wan
authors.affiliation: Department of Radiology, Tuen Mun Hospital, Tuen Mun, Hong Kong.
authors.forename: C Y
authors.initials: CY
authors.lastname: Lee
authors.affiliation: Department of Radiology, Kwong Wah Hospital, Hong Kong.
authors.forename: C Y
authors.initials: CY
authors.lastname: Lui
authors.affiliation: Department of Radiology, Kwong Wah Hospital, Hong Kong.
authors.forename: C Y
authors.initials: CY
authors.lastname: Fong
authors.affiliation: Department of Radiology, Kwong Wah Hospital, Hong Kong.
authors.forename: K C H
authors.initials: KC
authors.lastname: Lau
mesh_terms: D000328:Adult; D000368:Aged; D001940:Breast / Q000473:pathology*; D001943:Breast Neoplasms / Q000473:pathology*; D003287:Contrast Media; D003937:Diagnosis, Differential; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D006801:Humans; D007089:Image Enhancement; D008875:Middle Aged; D012372:ROC Curve; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity
chemical_list: D003287:Contrast Media