Olfactory neuroblastoma (esthesioneuroblastoma): a light and ultrastructural study of two cases.

Olfactory neuroblastoma is a malignant neoplasm with a varied biological behavior. Its clinical course is unpredictable and there is no correlation between its microscopic features and biological behavior. The present study deals with light and ultrastructural characteristics of two cases of olfactory neuroblastoma of the nasal cavity. In one patient, the definitive diagnosis was established on the basis of ultrastructural features of the lesion. The most consistent fine structural findings were the presence of intracytoplasmic densecored neurosecretory granules, "true" and "pseudo-" rosettes, and the neuritic processes emanating from the tumor cells. On the basis of their biochemical, histochemical, and ultrastructural characteristics, olfactory neuroblastomas are similar to neuroblastomas arising from the adrenals or sympathetic nervous system. These findings, therefore, support the hypothesis that olfactory neuroblastomas are most likely of neural crest origin and thus belong to a group of neoplasms collectively known as "apudomas" or neurocristomas. The literature review strongly favors combined surgery and postradiation as the most effective treatment of olfactory neuroblastoma.