GSTM1 and esophageal squamous cell carcinoma: Although there is a degree of inconsistency and population sizes are relatively small (n = 45 and n = 234 [23,24]), ESCC risk is generally addressed by Asian studies and reported increasing ESCC risk for the homozygous GSTP1105Val and homozygous GSTM1*0 genotypes whereas some studies even conclude them to be independent risk factors for ESCC in China [25-27] and Brazil [28].