Diagnosis: Malignant Peripheral Nerve Sheath Tumors
• Although S100 stains most benign nerve sheath tumors, only about 50% to 70% of malignant peripheral nerve sheath tumors show some S100 immunostaining.
• Demonstration of collagen-IV surrounding individual cells is the immunohistochemical correlate of the ultrastructural demonstration of basal lamina surrounding lesional cells of malignant schwannomas.
• However, although highly sensitive, collagen-IV stains many other tumors, and diagnosis of MPNST depends on clinicopathologic correlation, and results of an immunohistochemical panel to evaluate for morphologic mimics of this lesion.
