Every year, cancer claims the lives of more than half a million Americans. Cancer is the second leading cause of death in the United States, exceeded only by heart disease.  One of every four deaths in the United States is due to cancer.  In 2007, the overall costs of cancer in the U.S. — including treatment and indirect mortality expenses (such as lost productivity in the workplace) — was estimated to be $226.8 billion. 
Cancer, known medically as a Malignant Neoplasm, is a broad group of diseases involving unregulated cell growth.  In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invading nearby parts of the body.  Tumors can grow and interfere with the digestive, nervous, and circulatory systems, and they can release hormones that alter body function. There are over 200 different known cancers that affect humans.