Intracranial MPNST with multivacuolated cells and hyaline globules: a case with ultrastructural findings.

A case of intracranial malignant peripheral nerve sheath tumor (MPNST) with uncommon features due to recurrence is reported. The primary tumor showed typical histopathological features of MPNST with wavy nuclei and S-100 positivity. The patient's latest recurrent tumor resembled undifferentiated sarcoma with lipoblast-like multivacuolated cells and hyaline globules (HGs). Ultrastructurally, the vacuolated spaces contained granular materials derived from cystic dilation of the rough endoplasmic reticulum. The HG consisted of round osmophilic inclusions with or without a limiting membrane. The HGs and lipoblast-like multivacuolated cells may have been caused by the degeneration of tumor cells in myxoid stroma and abundant vasculature.