TBX1 and chordoma: Notably, genotype frequencies of the brachyury rs2305089 SNP differed significantly between the chordoma group and the control group as 7 out of 8 patients with skull base chordoma (~88%) harbored the SNP at both heterozygous (G/A) and homozygous (A/A) genotypes (three and four cases for G/A and A/A, respectively), whereas only 39 out of 75 patients (~52%) in the control group harbored either G/A or A/A genotypes (32 and 7 cases, respectively) (Figure 3a).