title: Spontaneous olfactory neuroepithelioma in a domestic medaka (Oryzias latipes).
abstract: Tumors of the central nervous system in fish are rare, and only six cases of spontaneous olfactory neuroepithelioma have been reported. This is the seventh case, found in a medaka, Oryzias latipes. The tumor was noted near the right olfactory orifice and finally measured 1.5 mm in diameter. Histologically the tumor consisted of undifferentiated neuroblasts forming a few true rosettes. Mitosis was frequently observed. Tumor cells stained diffusely for neuron-specific enolase and sporadically for neurofilament proteins by immunohistochemical procedures. Additionally a few large tumor cells were positively stained for S-100 protein. Electron microscopy revealed that the tumor cells had extended cytoplasm in which parallel neurotubules and a few neuroendocrine granules were noted. In the perinuclear region, bundles of intermediate filaments and neuroendocrine granules were seen. Single cilia and a pair of centrioles were occasionally found, but no ciliated cells were found in this tumor. Some large tumor cells contained electron-dense intracytoplasmic inclusions which showed a crystalloid structure by high-magnification electron microscopy; however, this type of crystalloid has never been reported in neuronal tumors.
authors.affiliation: Department of Pathology, Keio University School of Medicine, Tokyo, Japan.
authors.forename: C
authors.initials: C
authors.lastname: Torikata
authors.forename: M
authors.initials: M
authors.lastname: Mukai
authors.forename: K
authors.initials: K
authors.lastname: Kageyama
mesh_terms: D000818:Animals; D005260:Female; D005393:Fish Diseases / Q000473:pathology*; D005618:Fresh Water; D008854:Microscopy, Electron; D018241:Neuroectodermal Tumors, Primitive, Peripheral / Q000473:pathology / Q000648:ultrastructure / Q000662:veterinary*