Lumbar spinal osteoblastoma mimicking a dumbbell radicular schwannoma

Spinal dumbbell tumors originate from nerve roots, usually growing within the spinal canal, the neural foramen and the extraforaminal compartment in the paraspinal region. We report a case of a 20-year-old man who presented with back pain radiating to his left lower limb mostly when in a supine position. Magnetic resonance imaging of the lumbar spine showed a dumbbell lesion at the L5-S1 neural foramen, with enlargement of the foramen and extension into the left paraspinal compartment. Although MR imaging studies were strongly suggestive of a dumbbell radicular schwannoma, the histological diagnosis was an osteoblastoma of the lumbar spine originating from the left L5 pedicle with intracanalicular, intraforaminal and extracanalicular extension. The presentation, imaging studies, intervention, pathology and differential diagnosis are described.