Olfactory neuroblastoma: an ultrastructural study.

The ultrastructural features of two olfactory neuroblastomas are reported. By means of light microscopy, one was well differentiated while the other was a poorly differentiated, small cell neoplasm. The latter case required ultrastructural examination to establish the diagnosis. Electron microscopy of human tumors for diagnostic purposes may be particularly helpful in deciphering small, round cell tumors. Catecholamines were not biochemically detected in a portion of recurrent tumor from Case 2. The significance of this is equivocal in view of the limited previous biochemical studies of this neoplasm. However, by both light and electron microscopy, the morphology of olfactory and sympathetic neuroblastomas are strikingly similar.