ESR1 and breast cancer: Similarly, common polymorphisms at breast cancer susceptibility loci will differentially impact on breast cancer risk in different ethnic groups, if they display different frequencies or different linkage disequilibrium patterns across populations, such as CASP8*D302H that is virtually absent in Asians [121], or the ESR1 locus at which different risk alleles SNPs have emerged in Asians and Europeans [100,103,125-127].