Voluminous free disk fragment mimicking an extradural tumor.

A 56-year-old man presented with a rare case of a voluminous herniated disc fragment mimicking an intraspinal extradural tumor on magnetic resonance (MR) imaging. He had experienced low back pain and sciatica in his right leg for 12 months, which exacerbated suddenly 4 days before admission accompanied by right quadriceps muscle weakness. MR imaging with gadolinium demonstrated a tumor-like longitudinal lesion, extending from the L1-2 to the L3-4 intervertebral disc spaces and occupying most of the right half of the vertebral canal. L2 and L3 laminectomy, as well as L2-3 right foraminotomy, were performed. We were prepared for an oncological operation, but instead, a huge disc fragment was removed en bloc from the right epidural space. The patient's postoperative course was uneventful and he demonstrated full neurological recovery within 2 months. Sequestrated lumbar disc fragments must be considered in the differential diagnosis of longitudinal extradural mass lesions in the spinal canal independently of their size. MR imaging with contrast medium can differentiate herniated disc from tumors and other epidural lesions. Nevertheless, nontypical sequestrated disc herniations are extremely rare and can be misinterpreted.