The document discusses cancer at a high level. It defines cancer as uncontrolled cell growth and describes how some cancers cause rapid growth while others are slower. Cancerous cells can spread through the body via the lymph nodes and tumors can be malignant, meaning they invade nearby tissues and metastasize. There are many causes of cancer including smoking, alcohol, viruses, chemicals and radiation. Cancers are named for where they begin and the type of cell. The direct cause of cancer is changes to DNA from environmental and genetic factors.