tumor progression tumor progression tumor progression is the third and last phase in tumor development. this phase is characterised by increased growth speed and invasiveness of the tumor cells. as a result of the progression, phenotypical changes occur and the tumor becomes more aggressive and acquires greater malignant potential. together with the progression, more and more aneuploidy occurs. this may be evident as nuclear polymorphism. mri scans of a patient with astrocytoma, showing the tumor's progression between the incidental finding in 2007 and the onset of phenotypical changes in 2014.