Intradural, Extramedullary Anaplastic Astrocytoma Arising From the First Sacral Nerve Root

Abstract

A 48-year-old woman presentedwith a 6-month history of lumbosacral pain with sciatic distribution and paresthesia in the left S1 dermatome. She showed no motor weakness or bladder or rectal dysfunction. The preoperativemagnetic resonance image (MRI) of the lumbar spine showed an intradural, extramedullary cysticmass extendingalong the left S1 nerve root through the intervertebral foramen (Figure 1). Thepatient underwentmicroscope-assistedneurosurgical tumor resection via a lumbar posterior approach. Intraoperatively, the tumor was regarded as a peripheral nerve sheath tumor. Histologic examination revealed a moderately cellular astrocytic glioma thatdiffusely infiltrated thenerve root (Figure2A). The tumorcellshadatypical,moderatelypleomorphicnuclei and formed a fibrillary glial matrix. Immunohistochemical analyses demonstrated positivity for glial fibrillary acidic protein and the R132Hmutant isocitratedehydrogenase 1 (IDH1) protein in the tumor cells (Figure2B).Many tumorcellsdisplayednuclear accumulationof the tumor suppressor protein p53. Immunohistochemical analysis for neurofilament proteins confirmed the infiltrative, intraneural tumor growth by demonstrating residual nerve fibers within the tumor tissue (Figure 2C). Based on the histologic and immunohistochemical features, thetumorwasclassifiedasanaplasticastrocytoma (WorldHealthOrganizationgrade III).Pilocyticastrocytomawasconsidered as a differential diagnosis. However, the infiltrative growth pattern, as well as the strong positivity for R132H-mutant IDH1 and the p53 positivity, argued in favor of a diffuse astrocytic glioma. Additional cranial and spinal MRI did not provide evidence of anaxial originof this unusually locatedanaplastic astrocytoma. The patientwastreatedwith local radiotherapy(6-weekcumulativedose, 60 Gy) and chemotherapy (temozolomide, 140 mg/d), given concomitantly to aswell as after radiotherapy (six 28-day cycles: 5days per oral application of temozolomide, 23 days paused). At the last follow-up visit 6months after the operation, no tumor progression was detected and no new neurological deficits were reported (Karnofsky Performance Status Scale, 80).