Malignant peripheral nerve sheath tumors (MPNST) are uncommon aggressive neoplasms, frequently associated with type I neurofibromatosis. This is the first case of intradural lumbar spine MPNST with intraoperative findings of associated subarachnoid hemorrhage (SAH). A 72-year-old man presented to the emergency department with severe acute low back pain. Neurological examination was unremarkable. Gadolinium-enhanced MRI of the lumbar spine showed an irregularly shaped intradural lesion extending from L3 to L5. The lesion exhibited a medium signal both on T1 and T2-weighted imaging with peripheral enhancement. Through an L3-L5 laminectomy, a diffuse SAH, and a tumor tightly adherent to cauda equina nerve roots were found. Specimen examination revealed a fusocelular tumor with pleomorphic and hyperchromatic nuclei, positive for S100, and SOX10. On an 8-month follow-up, he had no neurological deficit, with a Karnofsky performance score of 90 points. Surgical evidence of SAH in lumbar spine intradural MPNST is a novel finding.

Los tumores malignos de la vaina del nervio periférico (TMVNP) son raros, agresivos y suelen asociarse con neurofibromatosis tipo I. Presentamos el primer caso de un TMVNP lumbar intradural con hallazgos intraoperatorios de hemorragia subaracnoidea (HSA). Un hombre de 72 años consulta a urgencias con intenso dolor lumbar, pero con examen neurológico normal. En la RM contrastada con gadolinio, se observó una lesión irregular intradural que se extendía de L3 a L5 con señal intermedia en T1 y T2, con captación de contraste periférico. Durante la laminectomía de L3-L5, se encontró HSA difusa y un tumor adherente a los nervios de la cauda equina. El espécimen tumoral mostró núcleos pleomórficos e hipercromáticos positivos para S100 y SOX10. Tras 8 meses de seguimiento, el paciente carece de déficit neurológico y puntúa 90 en la escala de rendimiento Kanofsky. La evidencia de HSA en TMVNP intradural lumbar es un hallazgo novedoso.