Table 1.

Histopathologic diagnostic criteria for MPNST

Pattern
Sweeping fascicles of spindle cells with densely cellular fascicles alternating with hypocellular myxoid zones Nodular, curlicue or whorled arrangement of spindle cells Heterogeneous differentiation
Cellular features
Atypical spindle cells with irregular contour Wavy, buckled or comma-shaped nuclei Cytoplasm usually indistinct and lightly stained
Subtle features characteristic of MPNST
Neoplastic cells appear to herniate into the lumen due to the eculiar proliferation of tumor cells in the sub-endothelial zone of vessels Proliferation of small vessels in the walls of large vessels Presence of neurofibromatous component (more evident in patients with NF-1) Geographic necrosis with pseudopalisading (this characteristic pattern of necrosis results from the persistence of viable perivascular cuffs of tumor cells)