<qa>  What is the genetic damage that underlies the development of cancers?Cancer arises due to genetic alterations that disrupt numerous cellular functions including proliferation, programmed cell death and senescence, that ultimately control the number of cells in a population. The genetic damage that underlies the development of cancers has a diverse etiology and loss of DNA repair mechanisms also may play a role in allowing mutations to accumulate. Cancers are also characterized by the ability to invade surrounding tissues and to metastasize. Many of the molecular alterations involved in this process have yet to be elucidated. 