NCIt definition : A pathologic process in which alterations at the molecular level result in a more
aggressive cytologic and phenotypic profile and clinical course of a neoplasm.;
NCIt note : The process of tumor progression is thought to be driven by clonal evolution. The
initiating event is a mutation that gives a cell the ability to divide when it shouldn't.
As a result a small group of related cells, called a clone because they are identical
to each other, grows. Clonal evolution occurs like a tree with mutations causing many
clones to branch off continuously.;