RIF1 and breast cancer: However, for basal breast cancer, RIF1 Exon 31 is not within the cohort of Cancer-Altered Short exons, because with a ΔPSIav value of 0.02 (Figure 2B), its level of inclusion is only marginally changed in basal cancer compared to normal tissue (since its ΔPSIav lies between −0.1 and 0.1).