Spinal nerve sheath myxoma (neurothekeoma).

Nerve sheath myxoma (NSM) is a rare, benign tumor of predominantly cutaneous location. They usually arise from small cutaneous nerves in the head, neck, and extremities, but exceptionally they arise from spinal nerve roots. Only three cases of intraspinal NSM have been reported. Herein is describe two additional cases of spinal NSM. The patients were 64-year-old and 31-year-old men who presented with low back pain. Spine magnetic resonance imaging showed small intradural extramedullary masses at the L2-3 level. Both tumors had typical histological features of myxoid-type NSM. The tumors had a strong immunoreactivity for vimentin, S-100 protein, and neuron-specific enolase and focal expression of epithelial membrane antigen and phosphorylated neurofilament. Ultrastructural observation of tumor cells with perineurial, fibroblast-like, and Schwann-cell differentiation suggests an origin from nerve sheath precursor cells.