Cancer is a group of diseases involving abnormal cell growth with the
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 bowel movements. While these symptoms may indicate cancer, they can
also have other causes. Over 100 types of cancers affect humans.
Tobacco use is the cause of about 22% of cancer deaths. Another 10% are due to
obesity, poor diet, lack of physical activity or excessive drinking of
alcohol. Other factors include certain infections, exposure to ionizing
radiation, and environmental pollutants.