E1726. Pearls and Pitfalls of Using DWI-ADC Imaging in Breast MRI with Pathologic Correlation
  1. Julie Senne; Missouri University
  2. Joel Schmidt; Missouri University
  3. Juhi Koolwal; Missouri University
  4. Derek Staner; Missouri University
Diffusion Weighted Imaging (DWI) in conjunction with apparent diffusion coefficient (ADC) sequence are increasingly utilized sequences in breast imaging that can improve the specificity of contrast enhanced (CE) Breast MRI. Invasive carcinomas of the breast generally restrict the relative free diffusion of water molecules, which make them hyperintense and easily identifiable on DWI. However, not all malignancies in the breast will restrict diffusion. Conversely, not every mass in the breast that restricts diffusion represents a malignancy. Our purpose is to bring attention to the most common false positive and false negative masses/nonmass enhancement when interpreting DWI of the breast in conjunction with CE Breast MRI.

Educational Goals / Teaching Points
Review false positive and false negative findings on DWI MRI by providing specific case examples of the most common benign breast masses that mimic malignancy on imaging, and malignant breast masses that fail to demonstrate characteristic restricted diffusion associated with breast malignancies. Histopathologic correlation for each case is provided. False positive diagnoses that can mimic malignancy on Breast MRI DWI include sclerosing adenosis, intrammamary lymph node, hematoma, cellular fibroadenoma, and granulomatous mastitis. False negative diagnoses that may fail to be +DWI / ADC include mucinous carcinoma, lobular carcinoma and ductal carcinoma in situ (DCIS).

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
The DWI/ADC sequence is typically used in conjunction with contrast enhanced (CE) MRI of the breast to increase the specificity of CE Breast MRI. However, false positive and false negative findings still exist. False positives arise because there are histologic patterns of tissue in the breast other than malignancies, that restrict the diffusion of water. Both crowding of cells of any type and abundant extracellular matrix can result in restricted diffusion (DWI/ADC+), mimicking a breast malignancy. This may lead to an unnecessary percutaneous biopsy or a biopsy result misinterpreted as discordant with imaging, leading to an unnecessary surgical biopsy. Radiologists familiar with benign histopathologic entities that are DWI/ADC+ may be able to avoid additional or unnecessary biopsies. Conversely, false negatives arise because some breast malignancies do not demonstrate a densely packed arrangement of malignant cells, and thus will not restrict the diffusion of water. Radiologists should not be dissuaded by lack of +DWI/ADC correlation when considering biopsy of suspicious enhancing masses on CE MRI.

Breast MRI DWI is a helpful adjunct to Contrast Enhanced Breast MRI that can increase the specificity of Breast MRI. However, radiologists should be aware of the pitfalls of DWI/ADC imaging, including both false positive and false negative masses/nonmass enhancement. This knowledge may prevent unnecessary biopsies and missed breast cancer diagnoses.