Spinal meningeal melanocytoma in the S-1 nerve root sheath with paraspinal extension mimicking schwannoma.

Background: Spinal melanocytomas are variants that can be extradural or intradural and are most often located in the intradural extramedullary compartment of the main thecal sac as in schwannomas. However, origin of this variant from the pure peripheral compartment of rootlets is exceedingly rare.

Case Description: The authors present a case of spinal melanocytoma with confusing pathologic and radiologic features. This patient presented clinically with severe radiating pain on the right lower extremity. Before surgery, clinical and radiologic findings were consistent with a schwannoma. However, on operation, a coal-black pigmented lesion mimicking old blood clot was found inside the right S-1 root sheath, attached to the dura. The mass was completely removed and consequently the patient's symptoms improved.

Conclusions: The spinal melanocytoma should be included as a differential diagnosis before giving a presumptive diagnosis of schwannoma or hemorrhage for the patient with a space-occupying lesion at a peripheral rootlet. Intraoperative gross morphology and histopathologic findings facilitate differential diagnosis.