Tumors specimens used in this study will be taken from tissues biopsied from patients with breast, colon cancer, sarcomas or melanoma as part of their routine care. Patients in the study will be among those receiving care at the: Department of Oncology, University Hospital, University of Lund, Sweden (breast cancer); Department of Medicine, University of Michigan, Ann Arbor, Michigan (breast cancer); Surgery Branch, National Cancer Institute, Bethesda, Maryland (melanoma), Johns Hopkins Univ. (colon cancer), Memorial Sloan Kettering (sarcoma).