Ultrastructural evidence for neural crest origin of the malanotic neuroectodermal tumor of infancy.

A case of malanotic neuroectodermal tumor of infancy, which occurred in the anterior maxilla of a 3-month-old girl, was studied by electron microscopy. Polymorphic cellular elements were revealed to be present: large melanin-producing cells with some of the characteristics of a neuroepithelium, small non-pigmented cells resembling immature neuroblasts, and many intermediate forms resembling differentiating neuroblasts. All cell types clearly demonstrated ultrastructural features of neurogenic cells, e.g. neurite-like cytoplasmic processes, fine filaments and microtubules indistinguishable from those seen in normal neurites, synaptic-like structures, and neurosecretory-like vesicles. Based on these fine structures, the lesion was presumed to represent a hamartoma of primitive neuroectodermal cells with a tendency toward the differentiation into melanin-producing cells. The neural crest origin of this tumor was convincingly supported by ultrastructural analysis.