The magnitude of the ''chromosomal chaos'' is also evident from comparative genomic hybridization (CGH) studies which show significant variations in the copy number of individual chromosomal segments. 'Chaos' is really a very appropriate word to describe what we observe from CGH data. The genomic changes are not distributed uniformly at random. 'Chaos' has been described by some researchers as ''a kind of order without any periodicity''. Some common changes seem to consistently appear in several independently arising tumours of the same type, and sometimes the researchers suggest common links [619] . Our work has addressed, in part, this question: ''Can we quantify the chaos observed in the genome from the increasingly available transcriptional data and relate it to tumour progression?'' If no commonalities were observed, we would not have found interesting biomarkers that seem that strongly correlate with the divergences from normal tissue types. We know from our results that these commonalities do occur.