The document discusses how normal cells are transformed into cancer cells through multiple genetic changes over many years. It describes several key changes that occur during this process, including immortalization where cells can divide indefinitely, transformation where cells grow independently of external signals, and metastasis where cancer cells invade other tissues. Several types of genetic alterations are also discussed that can activate oncogenes or inactivate tumor suppressor genes, such as mutations, amplification, insertion, or translocation events. This leads to deregulated cell growth and proliferation by disrupting normal cell signaling pathways.