Cancer is a group of diseases associated with abnormal cell growth with potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread.  Possible signs and symptoms include a lump, abnormal bleeding, prolonged cough, unexplained weight loss, and a change in stool.  Although these symptoms may be related to cancer, they may also have other causes. Over 100 types of cancers affecting humans.

Tobacco use is responsible for approximately 22% of all cancer deaths. Another 10% is due to obesity, poor diet, lack of physical activity or excessive alcohol consumption. Other factors include certain infections, exposure to ionizing radiation and environmental pollutants. In developing countries, 15% of cancers are due to infections such as Helicobacter pylori, Hepatitis B, Hepatitis C, Human papillomavirus infection, Epstein-Barr virus and virus human immunodeficiency (HIV).  These factors act, at least in part, by modifying the genes of a cell.  Generally, many genetic changes are necessary before the development of cancer.  About 5 to 10% of cancers are due to hereditary genetic abnormalities in a person's parents . Cancer can be detected by certain signs and symptoms or screening tests.