MKI67 and malignant peripheral nerve sheath tumor: The PRC2-isogenic M3 cells, when orthotopically transplanted into the sciatic nerve pockets of immunodeficient NSG mice, gave rise to high-grade MPNSTs with histological (e.g., monotonous spindle cell morphology, herringbone pattern, and fascicular growth) and immunostaining (e.g., H3K27me3 and Ki67 staining) features resembling those of high-grade human MPNST (13) (Supplemental Figure 2A).