Malignant growth of cells is often characterized by disorganization of tissue structure, abnormal blood vessel development, and insuffi- cient vascular supply. As a consequence, the cancer cells grow in a three-dimensional pattern in atypical microenvironments which include physical, chemical, and nutritional stresses. Necrosis often develops some distance away from the blood vessels. In association with an inherent instability in malignant cell populations, and also because of the changing micromilieu, significant cellular heteroge- neity emerges with regard to various phenotypic...