Revised: August 22, 2013
Accepted: August 28, 2013
Published online: September 28, 2013
Malignant peripheral nerve sheath tumor (MPNST) is an uncommon sarcoma which arises from pluripotent stem cells of the neural crest and differentiates predominantly towards Schwann cells. Low grade spinal MPNST with skeletal muscle differentiation (malignant triton tumor) is vanishingly rare. In this study, we report a case of a 53-year-old female with a homogenously enhancing C2-C4 extradural lesion. The lesion demonstrated a biphasic histologic pattern with a diffusely infiltrating, atypical spindle cell component strongly positive for vimentin and focally positive for S-100. The second component consisted of diffusely scattered clusters of mature skeletal muscle cells which were positive for desmin, fast myosin and muscle specific actin but negative for Myogenin and MyoD-1. The Ki-67 labeling index was low (< 1%) and no necrosis was identified. The present case is remarkable because of its rare location, low grade histology and unusual immunophenotype of the skeletal muscle component, which were not previously described.
Core tip: Malignant peripheral nerve sheath tumor (MPNST) is an uncommon sarcoma with dismal prognosis. Low grade MPNST with skeletal muscle differentiation (malignant triton tumor) in cervical spine is vanishingly rare. The present case is remarkable because of its rare location, low grade histological features and unusual immunophenotype of the mature skeletal muscle component, which were not previously described. Thus, our study expands the morphological spectrum and the clinicopathological significance of this uncommon tumor. These novel findings should be interesting to the neuropathologists, neurologists and neurosurgeons.