Correlation between mRNA expression level of full-length p53 versus Δp53 in breast carcinomas with various p53 mutations. p53 and Δp53 mRNA expression levels of mutated p53 in human breast tumors are shown with p53 relative mRNA expression in a.u. (arbitrary units) on x-axis and Δp53 on y-axis. Different mutation types are indicated by various symbols. "Mutational hybrids", mutations represented on full-length p53, but removed in Δp53, are marked with open symbols. Mutations present in both isoforms are specified with filled symbols. The shape of the symbols indicate the various mutation types: ■, □ missense mutations, ◊ in frame mutations, ▲, Δ nonsense mutations, * frame shift mutations, ● splice mutations, - mutations in the splice cassette (the two samples full-filling this criteria are highlighted with their sample ID). Horizontal lines show borders between the median values of the relative mRNA expression subgroups: MII vs Wt vs MI. The regression line for missense mutations is drawn with an equation y = 1.03x - 0.12 and a regression coefficient of 0.89. (1 low p53 value in this sample might be due to mutation in p53 primer binding site, 2 low Δp53 value in this sample might be due to mutation in Δp53 primer binding site – for details see Additional file 2).