Etiology
•The exact cause of cancer is unknown
•Theory: multi-step process of initiation, promotion, and progression that involves an interaction between environmental, genetic, and immunologic factors
• Initiation: exposure to a carcinogen that causes genetic damage and leads to cellular mutations
• Promotion: carcinogens alter the body's internal environment to promote the growth of mutated cells
• Progression: further changes to cellular DNA allows for tumor invasion into normal tissue and eventually metastasizes