melanotic neurilemmoma
A rare circumscribed, non-encapsulated and grossly pigmented nerve sheath tumor. It is composed of cells with the immunophenotypic and electron microscopic features of Schwann cells which contain melanosomes and are positive for melanoma markers. It usually involves spinal nerve roots but may occur in other locations. It may be associated with PRKAR1A gene mutation and Carney complex. Malignant behavior has been reported in a significant number of patients.