Melanotic schwannoma. Clinical and ultrastructural studies of three cases with evidence of intracellular melanin synthesis.

Three cases of intradural extramedullary melanotic nerve sheath tumors involving spinal nerves are reported. Clinical, roentgenographic, surgical, gross, histologic, and electron-microscopic findings were remarkably similar. Electron-microscopic study of the three neoplasms showed that the individual cells contained melanin pigment in all stages of maturation; in addition, there was prominent basal lamina, micropinocytotic vesicles, and other ultrastructural features consistent with Schwann cell derivation. The total clinical, operative, and morphologic picutre in these cases suggests that the tumors are true melanotic schwannomas capable of intracellular pigment production. The potential of such tumors for recurrence and metastasis is discussed.