Electron microscopy of glandular Schwannoma.

This report is the first description of the ultrastructure of the glandular elements in a so-called glandular Schwannoma (malignant peripheral nerve sheath tumor with glandular elements). The appearance of this uncommon tumor was typical by light microscopy. Electron microscopy of the sarcomatous component revealed features consistent with Schwann cell origin. Ultrastructure of the glands revealed a well-differentiated epithelium with basement membrane, desmosomes and the presence of microvilli with core rootlets, glycocalyx, and intracytoplasmic R-bodies. No cilia or blepharoplasts were present, arguing against ependymal origin of these glands. The microvilli with core rootlets, the glycocalyx and the R-bodies indicate the glandular epithelium was of the "intestinal type." The basis for the presence of such epithelium in Schwann cell neoplasms is uncertain, but pathologic induction-interaction between neural crest and mesenchyme may be the most plausible explanation.