Before revision:  This fact is manifested as heavy tails in the gene expression distribution functions . The tails are heavier -- i.e. the fraction of genes and the expression levels vary much more -- in tumors than in bacteria. Different tissue tumors show remarkably similar tails, indicating a kind of universality in cancer phenomena .
After revision:  This fact is manifested as heavy tails in the gene expression distribution functions by their maximal and minimal differential expression values and the exponents of the Pareto laws describing the tails .