GSTM1 and neoplasm: No significant differences in the frequency of the NK-3 haplotype from the Hb-2 block were found between SSM and NM histological subtypes or tumor thickness >1mm, although the frequency found in patients with ulceration (0.000, p < 0.05, Pc = 0.28) was lower than in patients without ulceration (0.046) (Table 6).