Primary intraosseous malignant peripheral nerve sheath tumor of spine with a giant paraspinal and retrospinal subcutaneous extension

Abstract

Background: According to World Health Organization (WHO) classification of tumors, malignant peripheral nerve sheath tumors (MPNST) encompass the tumors, which were previously termed as malignant schwannoma, neurogenic sarcoma, and neurofibrosarcoma. These are rare tumors constituting only 5% of all malignant soft tissue tumors. As per their name, they arise from the malignant proliferation of cells forming sheath of a nerve root. They cause spinal cord compression, secondary changes in the surrounding bone with variable amount of tumor tissue going into the paraspinal space. However, purely intraosseous origin of the MPNST with no visible connection with a nerve root or dura is rare and few cases have been described in the literature.

Case description: We present a primary intraosseous MPNST arising from the body of a thoracic spine with a minimal intraspinal component. However, there was a huge tumor part occupying the paraspinal and retrospinal region. The latter component was so large that it extended to lie just beneath the skin. The intraspinal component was confined to only one level. The giant extraspinal part was spanning multiple corresponding spinal level. We could not find such presentation in the literature.

Conclusion: Gross total removal (GTR) followed by adjuvant chemo-radiotherapy is the optimal treatment for MPNST of spine. In case of multiple laminectomy or gross spinal instability, spinal instrumentation makes the treatment protocol complete.

Keywords: Intraosseous; malignant peripheral nerve sheath tumor; paraspinal; spine.

Figure 1

(a) Contrast sagittal image showing the L3 vertebral body collapse with a giant tumor component lying in retrospinal space. (b) Coronal contrast image showing extension of the tumor to both paraspinal spaces. (c) Axial contrast showing involvement of the L3 body with tumor coming out of the spinal canal through both side intervertebral foramina. Note there is no tumor at L4 intervertebral foramina. (d) T2 sagittal image

Figure 2

(a) Large extension of the tumor lying in subcutaneous plane. (b) Tumor specimen in piecemeal

Figure 3

(a) Densely cellular fascicles alternating with hypocellular myxoid zones (×200). (b) Spindle shaped cells in a vague storiform pattern (×200). (c) Cells have irregular contours with eosinophilic cytoplasm with wavy, buckled, comma-shaped nuclei (×400). (d) Cells showing pleomorphism, prominent nucleoli (×400). (e) Perivascular accentuation of tumor cells (×200). (f) Negative GFAP immunostaining. (g) Strong Ki-67 immunopositivity (×400)