Melanoma arising in and limited to a spinal nerve root of the cauda equina.

Sir: A total of 39 cases of primary spinal cord melanoma have been described in the English language literature, but there are only two examples 1,2 of a melanoma arising in and limited to the spinal nerve root. We present a case of primary melanoma located in a spinal root of the cauda equina which was totally intradural, a peculiarity previously unreported. A 26-year-old man with a 3-month history of progressively worsening left sciatica, which failed to respond to medical treatment, was admitted for evaluation by the Department of Neurosurgery. Neurolog-ical examination showed no spinal cord compression. Magnetic resonance imaging revealed a single intra-dural mass at the level of the L3 vertebra, with no associated compression of the conus medullaris (Figure 1). An L3 laminectomy was performed, and after the dura was opened the tumour was exposed. It was a firm, nodular, black, apparently encapsulated mass arising in a spinal nerve root of the cauda equina. The tumour was totally excised together with proximal and distal segments of the involved spinal nerve root. Soon after surgery the sciatic pain disappeared. Macroscopically the tumour, which was 20 mm in diameter, was a rubbery, well-demarcated, round mass, with alternating black and white areas on section. Microscopically, it consisted of a diffuse proliferation of epithelioid and fusiform neoplastic cells showing marked nuclear atypia, with prominent eosinophilic nucleoli. Atypical mitoses were very frequent (16 mitoses ⁄ 10 high-power field), but there was no necrosis (Figures 2, 3 and 4). There was abundant Figure 1. Magnetic resonance image. Intradural mass at the level of the L3 vertebra. Figure 2. Low magnification. Well-demarcated nodular tumour with lobular pattern. Alternating pigmented and non-pigmented areas. Figure 3. Neoplastic non-cohesive cells with nuclear atypia and abundant atypical mitoses. Intracytoplasmic melanin pigment (top right corner).