ABSTRACT
Cancer is a group of diseases that result from uncontrolled growth and spread of genetically altered cells. Cancers are caused by both external factors (tobacco, infectious organisms, radiation, and chemicals) and internal factors (inherited mutations, hormones, immune conditions, and metabolic abnormalities). Interactions among these causative factors are thought to lead to genetic changes that transform normal cells into those that no longer respond to the normal homeostatic mechanisms enjoyed by normal tissue. At least two external factors are controllable, and, were they to be eliminated, a large number of cancers could be prevented. The use of tobacco products and excessive body fat contribute greatly to the incidence of several of the most serious forms of cancer.
