We describe a rare case of the cauda equina syndrome caused by a primary pleomorphic liposarcoma of the lumbar spine.

A 35-year-old man presented a 2-month history of back pain and slowly progressive weakness of lower limbs without sphincter dysfunction. It had a laminectomy for a supposed disc herniation three years previously. A diagnosis of recurrence hernia or fibrosis was discussed.

Magnetic Resonance Imaging (MRI) and CT scan of the lumbar vertebral column shows diffuse involvement of L4/L5 vertebral bodies, and an intradural lesion surrounding the nerve roots of cauda equina. The tumor occupied almost the whole width of the spinal canal. The diagnosis of plasmocytoma or metastasis was advocated and the patient was managed by an extended posterior approach in emergency. Histopathological findings revealed a pleomorphic liposarcoma. The patient received a course of radiotherapy and unfortunately he died at 3 months follow-up.

In spite of his unusual location in the spine, pleomorphic liposarcoma should be considered in the differential diagnosis of primary spinal tumors.