Melanotic Neuroectodermal Tumor of Infancy


Melanotic neuroectodermal tumor of infancy has been classified both as a hamartoma and as a benign neoplasm, with recent authors favoring the latter etiology.It is a rare tumor, occurring both orally and extraorally (usually in children under 6 months of age) and showing a characteristic biphasic histologic picture of melanin-containing epithelial cells lining slitlike spaces and small round cells resembling neuroblasts.
Its origin is probably the neuroectoderm (the embryonic layer that contributes greatly to cranial and oral development) although its gnathic location has led some authors in the older literature to consider it to be of odontogenic origin and to use such synonyms as “melanotic ameloblastoma” and “pigmented epulis.” Theories that assign its origin to ectopic retinal epithelium have produced the synonyms “retinal anlage tumor” and “melanotic progonoma.” Recent immunohistochemical studies confirm that it is a tumor with “polyphenotypic expression of neural and epithelial markers, melanin production, and glial and rhabdomyoblastic differentiation.”The lesion usually protrudes into the mouth and may also involve underlying bone. The lesion does not necessarily appear pigmented clinically. It is rarely an aggressive lesion although aggressive behavior with recurrences after local excision have been described.
Findings on magnetic resonance imaging (MRI) have been recently described.