What is Cancer?

Cancer is a group of diseases characterized by uncontrolled cell division leading to growth of abnormal tissue. It is believed that cancers arise from both genetic and environmental factors that lead to aberrant growth regulation of a stem cell population, or by the dedifferentiation of more mature cell types.

en.wikipedia.org/wiki/Cancer

Diseases in which abnormal cells divide and grow unchecked. Cancer can spread from its original site to other parts of the body and can be fatal. See also: hereditary cancer, sporadic cancer

www.ornl.gov/sci/techresources/Human_Genome/glossary/glossary_c.shtml