PMC4898298_01
27-year-old man with MPNST. Supine radiograph of the abdomen reveals mild height loss of the L2 lumbar vertebral body, with indistinctness of the right lateral border, and nonvisualization of the right pedicle (arrow). These signs indicate a destructive lumbar spinal mass.
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Abdominal radiographs showed no evidence of abdominal pathology but did show obscuration of the right L2 pedicle, suggesting a lumbar spinal mass (Fig. 1, arrow).
27-year-old man with MPNST. Sagittal (A) and axial (B) CT images of the lumbar spine using bone reconstruction algorithm demonstrate a destructive lesion at L2 that involves most of the anterior vertebral body, both pedicles, and the right lamina. Adjacent disc spaces are normal.
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CT examination excluded appendicitis and confirmed a large, destructive, lytic lesion of the L2 vertebral body and right pedicle (Fig. 2A, B). There was associated narrowing of the central spinal canal as well as loss of definition of the normal fatty tissue boundary between the right psoas muscle and the lumbar spine (Fig. 2C). A small portion of the mass near the right L1-L2 neural foramen was hypoattenuating; it contained a central focus of higher attenuation, akin to a target sign (Fig. 2C, arrow).
27-year-old man with MPNST. (C) Axial contrast-enhanced CT image through L2 with soft-tissue reconstruction algorithm shows an expansile soft-tissue mass invading the anterior vertebral body and protruding posteriorly into the central canal, causing moderate central stenosis. There is loss of the normal fat plane between the spine and the right psoas muscle (white arrows). The lesion is primarily isoattenuating to muscle, and contains a small hypoattenuating round focus with central high attenuation (target sign, arrow).
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Magnetic resonance imaging (Fig. 3) further delineated an expansile soft-tissue mass diffusely invading the L2 vertebral body, filling the right L1-L2 neural foramen, and displacing the thecal sac posteriorly with near-complete obliteration of the CSF space. T1-weighted sequences, hyperintense on T2-weighted sequences, and avidly enhanced following administration of gadolinium. The neuroforaminal portion of the mass demonstrated a target-like appearance on T2-weighted sequences, with a hyperintense halo surrounding a central hypointense region (Fig. 3, arrow).
27-year-old man with MPNST. Sagittal T1-weighted (A), T2-weighted (B), and T1-weighted gadolinium-enhanced (C) MR images of the lumbar spine demonstrate a soft-tissue mass involving most of the L2 vertebral body. The mass is hypointense on T1, hyperintense on T2, and enhances with gadolinium.
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Angiography demonstrated a hypervascular mass at L2, and pre-operative tumor embolization was performed using coils and Gelfoam (Figure 4A-B, Figure 4C-D).
27-year-old man with MPNST. Axial T2-weighted MR images through the mass (D, E) demonstrate soft tissue filling the right L1-L2 neural foramen, extending anteriorly to involve most of the L2 vertebral body and both pedicles, and protruding posteriorly to displace the thecal sac, with near-complete obliteration of the CSF space. Arrow in (E) indicates the "MRI target sign.:
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The lesion appeared microscopically to arise from a neurofibroma (Fig. 5).
27-year-old man with MPNST. Representative runs from spinal angiogram. A, Right L1 injection shows a hypervascular mass centered at the right side of the L2 vertebral body. B, Right L1 postembolization injection shows occlusion of the arterial feeders at that level.
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This benign neurofibroma however, transitioned through histologic phases of increasing cytologic atypia, cell density, nuclear pleomorphism, and mitotic activity to become, in most sections, a hypercellular spindle-cell lesion (Fig. 6) with moderate differentiation and up to 26 mitotic figures per 10 high-power fields.
27-year-old man with MPNST. Representative runs from spinal angiogram. C, Right L2 injection shows that the hypervascular mass has multiple segmental and collateral feeders. Coils have already been placed at the L1 level on the right and the left. D, Right L2 postembolization injection shows successful occlusion of numerous arterial feeders supplying the tumor.
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S-100, CD34, and C-kit (Fig. 7B). Several foci of malignant osteoid formation were evident on Gomori trichrome staining (Fig. 7C).
27-year-old man with MPNST. Immunohistochemical examinations show diffuse positive immunostaining for p75 (A) and no significant immunostaining for C-kit (B).
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This benign neurofibroma however, transitioned through histologic phases of increasing cytologic atypia, cell density, nuclear pleomorphism, and mitotic activity to become, in most sections, a hypercellular spindle-cell lesion (Fig. 6) with moderate differentiation and up to 26 mitotic figures per 10 high-power fields.