A type of magnetic resonance imaging called diffusion weighted imaging (DWI) will be tested to define cancerous from non-cancerous lesions in the breast.

For this study, the investigators plan to evaluate DWI scans performed in women with breast lesions identified by conventional breast MRI. The investigators will determine whether an ADC threshold can be defined for distinguishing benign and malignant lesions on DWI, assess the difference in ADC cutoffs for mass and non-mass lesions, and investigate the potential improvement in accuracy using techniques such as nonzero minimum b-value (to remove perfusion effects in the ADC measures) and normalized ADC measures (to account for variations in water content and other factors).

Inclusion Criteria:

• Willing and able to provide written informed consent;
• 18 years of age or older;
• Successful completion of breast MR examination with DWI required by protocol;
• Undiagnosed breast lesion (BI-RADS 3, 4, or 5) identified on MRI. The BI-RADS assessment must refer to a focal finding within the breast (i.e. mass, non-mass, or focus) as opposed to diffuse processes (e.g. background parenchymal enhancement, skin thickening) or lesions outside the subcutaneous breast (e.g. axillary lymph nodes, focal skin lesions, osseous lesions, etc.).

Exclusion Criteria:

• Participants with current or recent history (within 6 months prior to the MRI) of chemotherapy for cancer;
• Neoadjuvant chemotherapy between MRI and confirmation of lesion outcome (study lesions must be biopsied prior to undergoing any chemotherapy);
• Pregnant (if a female is of childbearing potential - defined as a pre-menopausal female capable of becoming pregnant - confirmation of pregnancy status per the site's standard of practice should be done prior to MRI);
• Unwilling or not suitable to undergo MRI or use the contrast agent gadolinium.

see ACRIN data sharing policy : https://www.acrin.org/RESEARCHERS/POLICIES/DATAANDIMAGESHARINGPOLICY.aspx