GSTM1 and squamous cell carcinoma: In the GST group, the GSTM1 subtype was reported to correlate with cervical neoplasia and chronic obstructive pulmonary disease [30, 31], while GSTT1 subtype had a higher incidence or percentage of bladder cancer [32] and the GSTP1 Ile105Val polymorphism was related with squamous cell carcinoma (SCC) and colorectal cancer [33, 34].