8-Year Follow-up for Woman with Spinal Meningeal Melanocytoma in S1 Nerve Root: Case Report and Literature Review

Background: Primary melanocytic neoplasms in the central nervous system are rare lesions arising from leptomeningeal melanocytes. These lesions produce neural deficits that resemble those of a meningioma or a schwannoma radiologically.

Case description: A tumor around the left S1 root with an extension into the left paraspinal compartment was identified in a 32-year-old female with persistent left leg pain for 6 months. The tumor was hyperintense on T1-weighted image and hypointense on T2-weighted image with a homogeneous enhancement. The clinical features, radiologic presentations, treatment choice, and pathologic characteristic were illustrated. The treatment outcome was compared with those reported in the previous literature. The tumor was en-bloc resected with the S1 nerve root reserved. Grossly, the tumor was a soft, capsulated, well-circumscribed, black pigmented lesion. Immunohistochemistry revealed that the tumor cells were positive for HMB-45, S-100 protein, and vimentin. The patient's symptoms were greatly relieved postoperatively. No signs of local recurrence were observed.

Conclusions: Spinal meningeal melanocytoma inside the nerve root is rare and benign. It is difficult to diagnose and often misdiagnosed as schwannoma or meningioma. HMB-45 has been suggested as a significant marker for the diagnosis of meningeal melanocytoma. Complete surgical resection is recommended as the primary treatment. Radiotherapy, chemotherapy, and other treatments can be selected as adjuvant therapies, but their effects are controversial. The recurrence and metastasis rates also remain unclear.