 70 eligible subjects will be asked to undergo contrast-enhanced MRI studies of the breast containing the lesion. Subjects will be asked to fast for 6 hours prior to the imaging session. Each subject will be tested for glucose, and if the glucose is not too high, the subject will be injected with a dose of radioactive sugar fluoro-deoxyglucose which has been shown in other studies to accumulate in breast cancers. The subject will be asked to sit quietly for 30 minutes and to empty the bladder. The subject will then be asked to be re-examined in the MRI scanner with MRI contrast injection. The examination bed will be moved out of the MRI scanner and detectors of the radioactive sugar will be placed near the breast in order to obtain a positron emission mammogram for a 10-minute period. The subject will then leave the MRI suite. 