Intraspinal melanotic arachnoid cyst and lipoma in neurocutaneous melanosis.

A 22-year-old woman with neurocutaneous melanosis is reported in whom an intraspinal melanotic congenital arachnoid cyst and melanotic lipoma occurred at the same thoracic location. Such combined occurrence of lesions of the central nervous system, producing compression of the spinal cord, has not been noted in any previously reported case of neurocutaneous melanosis. The pathogenesis of these two unusual melanotic lesions is discussed in relation to the ectomesenchymal properties of the neural crest. The concurrent melanotic arachnoid cyst and lipoma, in juxtaposition, were demonstrated by a computed tomography scan in which the preoperative diagnosis of lipoma was possible through the density of the lesion.