Low grade spinal malignant triton tumor with mature skeletal muscle differentiation

Figure 1 Pre-operative magnetic resonance imaging of the cervical spine. On coronal (A) and sagittal (B) view showed an extradural soft tissue mass at C2-C4 levels. After debulking of the mass (C) and at 10 mo post-operative follow up (D) showed markedly decreased mass effect on the cervical cord.

Figure 2 Histopathology of the tumor. A: High-power micrographs show a spindle cell lesion with focally increased cellularity and nuclear atypia; B: Scattered clusters of mature-appearing, small round cells with moderately abundant eosinophilic cytoplasm (arrow head) resembling a skeletal muscle differentiation.

Figure 3 Immunohistochemistry. The spindle cells are diffusely and strongly positive staining for vimentin (A) and focally positive for S-100 protein (B); The small round cells with skeletal muscle morphology showed positivity of muscle specific actin (C); The Ki-67 immunostaining shows low labeling index (D).