The purpose of this study is to see if dynamic contrast enhanced (DCE) MRI imaging makes it possible to distinguish benign conditions of the breast from malignant tumors and provide better information than can be obtained with regular MRI. DCE MRI uses a new way of collecting and analyzing the images or pictures which provides doctors extra information not available with standard imaging methods. This includes information about the blood vessels of different breast diseases. Pictures produced this way look just like the regular MRI pictures. The DCE MRI adds another imaging sequence (another scan) to the MRI examination ordered by your physician to evaluate your breast lesion, thus increasing the exam time (extra 10 min). The information gained from doing the new test, the DCE MRI, will not be used in your treatment and will not affect the type of care you receive for your breast lesions.

Our aim is to perform dynamic contrast enhanced (DCE) MRI on 150 patients during their routine breast MRI examination at MSKCC. This will add extra 10 min scanning time to the routine examination. High resolution (submillimeter) parametric maps of pathophysiologic quantities, such as tumor vessel permeability, tumor perfusion, extracellular extravascular volume fraction, will be generated from the DCE MRI data. These results will be correlated with pathology to determine new pharmacokinetic threshold so that the negative predictive value for benign lesions is close to 100%. The improvement in diagnostic specificity may help to reduce unnecessary biopsies in the future.

Inclusion Criteria:

· scheduled for breast MRI interventional procedure for a known breast lesion.

Exclusion Criteria:

• patients who would be normally excluded from undergoing an MRI examination patients with a pacemaker, aneurysm clip or any other condition that would warrant avoidance of a strong magnetic field.
• patients who are unable to cooperate for an MRI, and/or have known reaction to gadolinium contrast agent.

Participants will be selected at the time of the MRI interventional procedure by the radiologist who is protocoling the MRI examinations and who is an investigator on this protocol. Any known breast lesion, benign or malignant, will be appropriate for evaluation with DCE MRI. Pathology results will be obtained for each patient as a result of surgery or MRI guided biopsy, allowing correlation between the pathology and DCE MRI data.