[Olfactory neuroblastoma. Clinical course, light microscopic and ultrastructural findings in 3 cases]

Olfactory neuroblastomas are considered to be a clinicopathological entity, but they may show variable histologic pictures. The light and electron microscopic features of 3 cases as examples for the possible range of morphological findings are presented. This report is also aimed at defining essential diagnostic features, at discussing the differential diagnosis and finally at making pathologists more familiar with these rare tumors. The clinical appearance of the three cases was more or less typical for olfactory neuroblastomas. The leading symptom in all patients was a nasal obstruction. Light microscopically, the neuroblast-like tumor cells were arranged in sheaths or nests. Only in case 1 there were some Flexner rosettes, and especially in case 2 numerous Homer-Wright pseudo-rosettes could be found. Somewhat spindled cells with resemblance to Schwann cells were recognized in case 1 and 3. Neither argyrophilia nor argentaffinity could be demonstrated. Neuroblast-like tumor cells in case 2 contained glycogen intracytoplasmically. The diagnostically essential electron microscopic characteristics were neurite-like cellular processes and neurosecretory granules within the cytoplasm. Corresponding to light microscopic findings in cases 1 and 3, cells with features of Schwann cells could be identified. From the literature and the results presented here the conclusion can be drawn, that in nearly all cases a definite diagnosis is possible if besides the histologic picture also clinical data and, if necessary, ultrastructural and immunohistochemical findings are considered. The most important light microscopic criteria are a fine-fibrillary intercellular substance and the occurrence of Homer-Wright pseudo-rosettes. The differential diagnosis of olfactory neuroblastomas with special regard to electron microscopic findings is discussed and some remarks on the clinical behaviour are added.