Giant Retroperitoneal Lumbar Schwannoma with Extensive Vertebral Body Erosion Managed Without Spinal Instrumentation:...

Background: Giant retroperitoneal schwannomas with vertebral body erosion are exceedingly rare, and the decision regarding spinal instrumentation following tumor resection remains controversial in the absence of established guidelines. A 25% vertebral body involvement threshold has been proposed as an indication for fixation, yet this criterion does not account for bone quality or the potential biological adaptation of bone to chronic mechanical loading. Case Presentation: A 56-year-old man presented with bilateral gluteal pain and urinary urgency secondary to a giant retroperitoneal lumbar schwannoma (97 × 67 mm) with 36.6% erosion of the L5 vertebral body, confirmed by CT-guided biopsy (S100+, SOX10+, Ki-67 < 5%). Despite erosion exceeding the proposed instrumentation threshold, complete tumor resection was performed via an anterior laparotomic approach without spinal fixation, based on the absence of clinical or radiological signs of instability and the integrity of the intervertebral disc and posterior ligamentous complex. Intraoperative neurophysiological monitoring guided sacrifice of the tumor-origin root. The postoperative course was uneventful, with complete resolution of symptoms and no new complaints or neurological deficits at one-year follow-up. Conclusions: Post-hoc Hounsfield Unit measurements on pre-operative CT demonstrated markedly elevated bone density at the eroded L5 vertebral body (480 HU) compared with the adjacent L4 vertebra (317 HU), consistent with compensatory sclerosis induced by chronic mechanical compression. Pre-operative HU assessment may represent a valuable, readily available adjunct to anatomical erosion criteria in the surgical decision-making process for giant schwannomas with vertebral body involvement.