NF1 and schwannoma: Upon loss of additional tumor suppressors (p53) in an NF1 null Schwann cells or Schwann precursor cells, schwannomas can transform into MPNST.[18] Histologically, MPNST diagnosis relies on the identification of necrosis within the tumor tissue, perivascular cell proliferation, spindle cells with hyperchromatic nuclei, and a marked increase in mitotic figures.[19] Histological examination in this case did not reveal evidence for MPNST.