An uncommon intramedullary tumor: Primary medullary cone melanoma

Melanoma is the third most common primary tumor to metastasize to the central nervous system (CNS). However, primary CNS melanoma is very rare, and primary intramedullary melanoma is even less frequently encountered, with only 27 cases published in the literature. There are no pathognomonic imaging characteristics, therefore, the diagnosis must be confirmed immunohistologically and the preferred treatment is the gross total resection.

A 68-year-old male presented with low back pain of 2 months duration, and 1 week of urinary retention/anal sphincter incontinence. The neurologic examination revealed bilateral paraparesis (3/5 level) with bilateral Babinski signs, and a T10-T11 pin level. The lumbar CT-Scan showed a hyperdense intramedullary tumor arising from the conus medullaris. The patient underwent a D12-L2 laminectomy with myelotomy for gross-total tumor resection. Postoperatively, he regained motor function but the urinary incontinence remained unchanged. The diagnosis of a primary malignant melanoma was confirmed both histopathologically and immunohistochemically (e.g., staining revealed positive immunoreactivity for S100 protein and Melan A).

Primary intramedullary spinal melanoma is very rare, and the diagnosis must be biopsy/operatively confirmed. Whether gross total resection is feasible depends on the extent of tumor infiltration of the cord/ adherence as well as the potential for clinical deterioration with overly aggressive removal.