ESR1 and breast cancer: Thus, the present study aimed to examine the genotypes of p53 Arg72Pro, MDM2 SNP309 T to G, p21 Ser31Arg, HER2 Ile655Val, ER SNP594 G to A, and FGFR2 rs2981582 and their allele frequencies in a clinical group of early onset and late onset BC patients and to test for any correlations between certain genotypes or alleles with the risk of developing early onset BC in Yogyakarta, Indonesia.