Although the small number of cases subjected to SF3B1 mutation profiling could have resulted in a type I or α error resulting in a higher frequency of mutations than the mutation rate in unselected breast cancers, the probability of finding three samples harbouring an SF3B1 mutation by chance is less than 0.5% (based on a binomial distribution assuming a mutation rate of 1.8% in unselected breast cancers). Here, SF3B1 is linked to breast cancer.