Cancer is a number of related diseases that are characterized by the uncontrolled proliferation and disorganized growth of cells. Tumor cells invade and destroy normal tissues and may spread throughout the body via the circulatory systems.

A Genetic Disease

Cancer is the result of changes in the genetic material of a cell that cause the cell to gradually lose the ability to grow in a regulated fashion. These changes can be brought about by contact with harmful environmental agents or by inheritance of genes leading to a genetic predisposition.

Cancer risk increases with age, as the probability of accumulating mutations in the DNA increases with time. Environmental factors include lifestyle (e.g., smoking), diet (e.g., saturated fats from red meat), and exposure to certain chemicals (e.g., asbestos, benzopyrenes), ionizing radiation (e.g., X-rays, radon gas), ultraviolet radiation (e.g., sun, tanning beds), and certain viruses (e...