Figure 2: Cancer Growth: Local and Global Influences. The initiation and growth of a cancer occurs locally and is largely due to accumulation
of genetic changes that lead to defects in the molecular machinery of cells, permitting them to multiply uncontrollably and survive when normal
cells would die (A and C)(see Sidebar on The Genetic Basis of Cancer). Uncontrolled proliferation occurs when normal control of a tightly
regulated cellular process called the cell cycle is lost (A). Interactions between cancer cells and their environment also strongly influence cancer
development and growth. For example, systemic factors in the circulation such as hormones and nutrients affect these processes (B), as does the
cancer’s ability to stimulate the creation of new blood vessels and lymphatic vessels to bring nutrients as well as escape to distant sites
(metastasize) (C) and its capacity to manipulate the immune system (D).