An unusual embryonal tumor of the nasal cavity in a neonate--a nasal blastoma? A clinical, histologic, and ultrastructural study.

We report the clinicopathological and ultrastructural features of a primitive embryonal tumor which occurred as a polypoid mass in the nasal cavity of a newborn infant. Its primitive-appearing, glycogen-rich, small round cells exhibited epithelial characteristics histologically, immunohistochemically, and ultrastructurally. The tumor was initially diagnosed as embryonal carcinoma because of evidence for endodermal differentiation and lack of specific features of other types of small round cell tumors of childhood. However, it did not have the characteristic features of endodermal sinus tumor nor the anaplasia of the adult type of embryonal carcinoma. It had some resemblance to embryonic somatic tissues and the blastemal component of some of the primitive tumors of childhood. Because of its unique morphological appearance, which has never been reported, and its relatively indolent behavior after chemotherapy and radiotherapy, we believe that this is a distinctive primitive teratoid tumor which may be classified as nasal blastoma.