GSTM1 and meningioma: Recurrent GSTM1 null genotype meningiomas harbored either a) zero copies of GSTM1 and two copies of GSTM2, indicating that GSMT1 deletions in this patient were congenital (variant A), or b) were GSTM2 hemizygous (variant B), suggesting that the loss of one GSTM1 copy was inherited while another copy of the gene was lost in these tumors due to somatic deletion of chr1p (Figure 4D).