A previously healthy 24-year-old male presented with a 3-month history of progressive backache and weakness in both legs. Magnetic resonance imaging of the spine showed a large soft tissue mass infiltrating paraspinal musculature of lumbosacral area, sacral laminas, last lumbar and all sacral vertebra, protruding into the spinal canal, and with propagation into pelvis. Baseline laboratory data were normal. Decompressive laminectomy and tumor removal were performed resulting in neurological improvement. Histological examination identified granulocytic sarcoma (GS). Bone marrow biopsy showed normal findings. The patient underwent adjuvant chemotherapy and radiotherapy, resulting in the elimination of residual lesion, followed by autologous transplant. Immediate diagnosis and adequate systematic treatment are essential to achieve optimal results in patients with isolated GS. The patient is alive and free of the disease 14 months from the diagnosis.