Fig. 1

Pathological findings including morphology, immunohistochemistry (IHC), and fluorescence in situ hybridization (FISH) of malignant peripheral nerve sheath tumor (MPNST) cases. a. MPNST with fascicular proliferation of spindle cells that had enlarged oval to spindle nuclei with moderate to severe nuclear atypia (NF1M-20). b. IHC for histone 3 trimethylated on lysine 27 (H3K27me3). The tumor cells were completely negative for H3K27me3 on IHC (NF1M-20). c. FISH for p16 deletion. The tumor nuclei showed heterozygous deletion of p16. Two green signals indicating a control locus and one red signal indicating a target locus were found (NF1M-20). d. Another case of MPNST also exhibited fascicular and storiform proliferation of spindle cells with enlarged spindle nuclei with moderate to severe nuclear atypia (NF1M-6). e. IHC for H3K27me3. A majority of tumor cells were positive for H3K27me3 on IHC, although H3K27me3-negative tumor cells were focally intermingled. The tumor showed partial loss of H3K27me3 (NF1M-6). f. FISH for neurofibromatosis 1 (NF1) deletion. Tumor nuclei showing heterozygous deletion of NF1. The number of red signals (two) for the target locus was less than the number of green signals (four) for the control locus (NF1M-6)