OUTLINE: This is a multicenter study. Patients undergo a high resolution 3D post contrast magnetic resonance imaging (MRI) scan. Patients with enhancing abnormalities undergo a dynamic scan no less than 18 hours later. Some patients may require a third scan if a core biopsy is to be performed. Patients who are ultimately found to have cancer are assessed for extent of cancer including measurement of the index lesion and identification of other present foci of cancer in relation to the index lesion. Further histological diagnosis of index lesions is determined by MRI-guided needle localization excisional biopsy. Patients with benign needle biopsy are followed for 2 years. Patients with benign primary lesions receive a follow up MRI scan 1 year after the initial scan. Patients with benign primary lesions and incidental enhancing lesions (IEL) are followed at 2 years. Patients with negative needle biopsies not yielding a specific diagnosis and who do not undergo subsequent excisional biopsy are followed yearly for 2 years.