Congenital primitive neuroectodermal tumor with epithelial and glial differentiation. An ultrastructural and immunohistochemical study.

A congenital primitive neuroectodermal tumor associated with epithelial and glial elements is described. This soft-tissue tumor present on the right temple of a newborn boy consisted mainly of small round cells of the primitive neuroepithelial type, occasionally forming rosettes. The other components were focal glandular structures producing mucin, and aggregates of epithelioid cells bearing clear cytoplasm, both being distributed throughout the entire tumor. Additional glandular and clear cell components were strongly positive for various epithelial markers, such as carcinoembryonic antigen, epithelial membrane antigen, and cytokeratin. Epithelioid cells were also positive for neuron-specific enolase and S100 protein. Glial differentiation was evidenced in some of the epithelioid cells by localization of cytoplasmic glial fibrillary acidic protein. These findings suggest that this tumor derives from a remnant of a neural crest, and the possibility of a special type of peripheral primitive neuroectodermal tumor is considered.