From U Washington: Nonmalignant Breast Lesions: Apparent Diffusion Coefficients of Benign and High-Risk Subtypes Assessed as False-Positive at Dynamic Enhanced MR Imaging

http://www.ncbi.nlm.nih.gov/pubmed/23033500

Radiology. 2012 Oct 2. [Epub ahead of print]

Nonmalignant Breast Lesions: ADCs of Benign and High-Risk Subtypes Assessed as False-Positive at Dynamic Enhanced MR Imaging.

Parsian S, Rahbar H, Allison KH, Demartini WB, Olson ML, Lehman CD, Partridge SC.

Source

Departments of Radiology and Pathology, University of Washington School of Medicine, Seattle Cancer Care Alliance, 825 Eastlake Ave E, G3-200, Seattle, WA 98109-1023.

Abstract

Purpose:To evaluate the diffusion-weighted (DW) imaging characteristics of nonmalignant lesion subtypes assessed as false-positive findings at conventional breast magnetic resonance (MR) imaging.

Materials and Methods:This HIPAA-compliant retrospective study had institutional review board approval, and the need for informed patient consent was waived. Lesions assessed as Breast Imaging Reporting and Data System category 4 or 5 at clinical dynamic contrast material-enhanced MR imaging that subsequently proved nonmalignant at biopsy were retrospectively reviewed. One hundred seventy-five nonmalignant breast lesions in 165 women were evaluated. Apparent diffusion coefficients (ADCs) from DW imaging (b = 0, 600 sec/mm(2)) were calculated for each lesion and were compared between subtypes and with an ADC threshold of 1.81 × 10(-3) mm(2)/sec (determined in a prior study to achieve 100% sensitivity).

Results:Eighty-one (46%) lesions exhibited ADCs greater than the predetermined threshold. The most prevalent lesion subtypes with mean ADCs above the threshold were fibroadenoma ([1.94 ± 0.38 {standard deviation}] × 10(-3) mm(2)/sec; n = 30), focal fibrosis ([1.84 ± 0.48] × 10(-3) mm(2)/sec; n = 19), normal tissue ([1.81 ± 0.47] × 10(-3) mm(2)/sec; n = 13), apocrine metaplasia ([2.01 ± 0.38] × 10(-3) mm(2)/sec; n = 13), usual ductal hyperplasia ([1.83 ± 0.49] × 10(-3) mm(2)/sec; n = 12), and inflammation ([1.95 ± 0.46] × 10(-3) mm(2)/sec; n = 10). Atypical ductal hyperplasia ([1.48 ± 0.36] × 10(-3) mm(2)/sec; n = 23) was the most common lesion subtype with ADC below the threshold. Lymph nodes exhibited the lowest mean ADC of all nonmalignant lesions ([1.28 ± 0.23] × 10(-3) mm(2)/sec; n = 4). High-risk lesions (atypical ductal hyperplasia and lobular neoplasia) showed significantly lower ADCs than other benign lesions (P < .0001) and were the most common lesions with ADCs below the threshold.

Conclusion:Assessing ADC along with dynamic contrast-enhanced MR imaging features may decrease the number of avoidable false-positive findings at breast MR imaging and reduce the number of preventable biopsies. The ability of DW imaging to help differentiate high-risk lesions requiring additional work-up from other nonmalignant subtypes may further improve patient care.