In the spontaneous MPNST mouse model, DMSO treated animals had approximately 50% low grade, neurofibroma-like tumors (grade 1-2) and 50% high grade (grade 2/3 and 3) tumors, as assessed by H & E, S100, and Ki67 as described above (Figure 3B & 5A). This evidence concerns the gene S100B and malignant peripheral nerve sheath tumor.