Melanin containing neurofibroma: case report with evidence of Schwann cell origin of melanin.

This case report describes a melanin-containing neurofibroma involving a spinal nerve root. Electron microscopy of the tumor shows that neoplastic Schwann cells are capable of melanogenesis. Although this capability is suggested in the literature, few reports provide ultrastructural confirmation. The likely identity between reported "cellular blue nevi of spinal nerve roots" and nerve sheath tumors is discussed. It is possible that pigmented nerve sheath tumors behave more aggressively than nonpigmented ones, although it is debatable.