Six polymorphisms in ESR1 (rs9340799, rs2234693, and rs3798759) and ESR2 (rs2077647, rs4986938, and rs1256049) genes were selected in the present study according to Tang et al [19 (link)] Peripheral blood samples were obtained from all subjects and analyzed the distributions of ESR1 and ESR2 genes polymorphisms in a Chinese Han population. Genomic DNA was extracted by standard phenol–chloroform method. Genotyping of the ESR1 and ESR2 polymorphisms was determined by the SNaPshot method. The GeneAmp 9700 polymerase chain reaction thermocycler (Applied Biosystems, Foster City, CA) was used for polymerase chain reaction. The 3730XL genetic analyzer (Applied Biosystems, Foster City, CA) was used for sequencing. GeneScan 3.7 Software (Applied Biosystems, Foster City, CA) was used for data analysis.