In the literature, separate analyses of the genes GSTT1 and GSTM1 are inconclusive regarding the risk of developing thyroid cancer.5 Our results from separate analyses of these genes are in accordance with the literature, although we observed the presence of GSTM1 in 72.2% (13/18) and GSTT1 in 88.9% (16/18) of the benign tumor cases. This evidence concerns the gene GSTM1 and thyroid cancer.