Melanotic neuroectodermal tumor of infancy.

Melanotic neuroectodermal tumor of infancy is a rare, neural-crest-derived neoplasm that is believed to be congenital. The tumor has a marked predilection for the head and neck--particularly the maxilla, where approximately 70% of these tumors are located. The anterior maxilla is most commonly affected. There is no predilection for either sex. Nearly all patients present with an enlarging mass, usually within a few years of birth. Intraoral lesions may appear "blue," suggesting the presence of pigment. Radiographic images will often show a destructive lesion with tooth displacement, but they are nonspecific. Laboratory studies show high urinary levels of vanillylmandelic acid.

Histologically, the tumor is characterized by a biphasic tumor cell population in a trabecular, tubular, or alveolar arrangement (figure, A). Larger pigmented cells surround groups of the smaller, round-to-oval, blue neuroectodermal cells (figure, B). The trabeculae are separated by a dense collagenous stroma. The periphery of the tumor is usually infiltrative into the surrounding bone or soft tissue. The large cells are epithelioid, cuboidal cells that line the exterior of the alveolar spaces or trabeculae. They demonstrate relatively large, vesicular nuclei with prominent nucleoli that are surrounded by eosinophilic cytoplasm with ill-defined cell borders. The cytoplasm contains variable amounts of medium- to dark-brown melanin granules (figure, B). The small, round-to-oval cells contain a hyperchromatic nucleus and scant cytoplasm. Immunohistochemically, both types of tumor cells are reactive to vimentin and neuronspecific enolase; the larger cells may also be reactive to keratin and HMB-45. The tumor must be differentiated from melanoma, olfactory neuroblastoma, lymphoma, and rhabdomyosarcoma. Rare examples of pigmented primitive neuroectodermal tumors may be included in the differential diagnosis.

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Complete surgical excision with histologically clear margins (0.5 cm) is the treatment of choice. However, complete extirpation is difficult to achieve, and postoperative bleeding and infection can complicate surgery. Recurrences develop quite frequently when the initial surgery is inadequate. The tumor's histologic appearance does not reliably predict its clinical course. Metastasis is rare.

Suggested reading

Barrett AW, Morgan M, Ramsay AD, et al. A clinicopathologic and immunohistochemical analysis of melanotic neuroectodermal tumor of infancy. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2002;93:688-98.

Gaiger de Oliveira M, Thompson LDR, Chaves AC, et al. Management of melanotic neuroectodermal tumor of infancy. Ann Diagn Pathol 2004;8:207-12.

Kapadia SB, Frisman DM, Hitchcock CL, et al. Melanotic neuroectodermal tumor of infancy. Clinicopathological, immunohistochemical, and flow cytometric study. Am J Surg Pathol 1993;17:566-73.

Brenda L. Nelson, DDS; Lester D.R. Thompson, MD, FASCP

From the National Naval Medical Center, Bethesda, Md. (Dr. Nelson), and the Department of Pathology, Woodland Hills Medical Center, Southern California Permanente Medical Group, Woodland Hills, Calif. (Dr. Thompson).