NOTE Pathology Olfactory Neuroepithelioma in a Dog: An Immunohistochemical and Electron Microscopic Study Kazuya HARA1), Akinori SHIMADA1), Takehito MORITA1), Masumi SAWADA1) and Takashi UMEMURA2) 1)Department of Veterinary Pathology, Tottori University, Tottori 680–0945 and 2)Laboratory of Comparative Pathology, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo 060–0818, Japan (Received 6 November 2001/Accepted 15 January 2002) ABSTRACT. A case of olfactory neuroepithelioma was investigated electron microscopically and immunohistochemically. The tumor mass was found in the nasal cavities of a 10-year-old female dog, which showed epistaxis, nasal discharge and facial swelling. The tumor tissue consisted of tubular structure of cuboidal to columnar cells and compactly arranged nests of small cells surrounded by a fibrovas- cular stroma. Mitotic figures were frequently observed. Immunohistochemically, the tumor cells frequently showed positive for neu- rofilament protein, synaptophysin and/or carnosine in addition to keratin. Ultrastructurally, tight junction was observed between the tumor cells. No dense-cored secretory granules were shown in the tumor cells. These findings indicated that the present tumor had neu- ronal and epithelial features probably originating from the olfactory epithelium. KEY WORDS: canine, neuroepithelioma, olfactory. J. Vet. Med. Sci. 64(4): 391–393, 2002 The olfactory neuroblastomas are uncommon, malignant In this report, we describe histological, immunohis- neoplasms, most of which arise in the esthmoturbinate tochemial and ultrastractural features of a spontaneous case region of the caudal nasal cavity. It is unclear whether they of olfactory neuroepithelioma in a 10-year-old female dog. arise from the olfactory neuroepithelial cells, remnants of A 10-year-old female mongrel dog, with a 2-month-his- neural crest cells, or local components of the dispersed neu- tory of epistaxis, nasal discharge and facial swelling was roendocrine system. Thus not only the histological diagno- brought to the Veterinary Clinic in Tottori University. X- sis but also the origin of the tumor is still a matter of ray examination demonstrated an oval to round mass, 3 cm controversy in humans as evidenced by the different terms in diameter, in the left nasal cavity. The mass destroyed used to describe the tumor [24]. These include olfactory nasal turbinates extending into the right nasal cavity beyond neuroblastoma [6, 8, 18], olfactory esthesioneuroblastoma the nasal septum. The animal was killed humanely because [4, 14], esthesioneurocytoma [2], esthesioneuroepithelioma of poor prognosis. A complete necropsy was performed. [3], olfactory neuroepithelioma [21], intranasal neuroblas- Samples of the solid mass, reddish white in color, were toma [19], and olfactory placode tumor [26]. Immunohis- taken and immersed in 10% neutral buffered formalin for tochemically, the tumor provided a variable number of cells histological examination. They were then dehydrated, positive for neurofilament protein, keratin, neuronspecific embedded in paraffin wax, sectioned at 4 µm, and stained enolase and S-100 [23]. Based on these findings, Hassoun with haematoxylin and eosin (HE). The mass in the nasal et al. [9] and Takahashi et al. [23] suggested that their cases cavity was tentatively diagnosed as an undifferentiated car- consisted of cells differentiating in at least two distinct cinoma. With the aid of labeled streptavidin-biotin kit directions, neuronal and epithelial, and concluded that the (Dako, Glostrup, Denmark), selected sections from the tumors were of true olfactory epithelium origin, or more tumor were assessed reactivity for cytokeratin, neurofila- precisely, derived from the bipotential, undifferentiated ment protein (NFP), synaptophysin, and carnosine which is basal cells of the epithelium and differed from olfactory a marker for the olfactory cells [17]. Polyclonal anti-carnos- neuroblastomas which are generally considered to be ine antibody (generous gift from Dr. Sakai, Department of “APUD (amine precursor uptake and decarboxylation) Anatomy, School of Medicine, Fujita Health University, tumors”. Based on these findings, the term of olfactory neu- Japan) was diluted at 1:2000. Monoclonal anti-cytokeratin roepithelioma was added in the category of olfactory neuro- antibody (Cytokeratin19, RCK108, Dako), anti-NFP anti- blastoma as a new variant in the WHO classification of body (2F11, Dako), and monoclonal anti-synaptophysin human tumors [20]. On the other hand, in the veterinary lit- antibody (SY38, Dako) were diluted at 1:50. Deparaf- erature, the term olfactory neuroblastoma (esthesioneuro- finized sections were pretreated with 0.3% H2O2-methanol blastoma) is still used in the WHO classification [10] as well for 30 min at room temperature and normal goat serum for as in case reports [1, 7] of the tumor in domestic animals. 30 min at 4°C. The sections were incubated with the pri- Detailed immunohistochemical and electron microscopic mary antibodies overnight at 4°C. Immunoreactivity was study on these tumors in the veterinary literature is limited. detected with diaminobenzidine (DAB) as chromogen. The sections were counterstained with methyl green. *CORRESPONDENCE TO: SHIMADA A., Department of Veterinary For ultrastructural study, formalin-fixed samples were Pathology, Tottori University, Tottori 680–0945, Japan. diced at 1 mm3, washed in 0.1 M phosphate buffer (pH 7.4) 392 K. HARA ET AL. Fig. 1. Light microscopy showing compactly packed round to spindle tumor cells with occasional glandular patterns. HE, × 380. for three hours, and post-fixed in 1% osmium tetroxide and Fig. 2. Tumor cells are immunoreactive for cytokeratin (a), neu- embedded in Epon 812. Ultrathin sections were cut, stained rofilament protein (b), synaptophysin (c) and carnosine (d). × with lead citrate and uranyl acetate, and examined on an Immunohistochemistry, 550. electron microscope (JEM-100CXII). The tumor showed combination of tubular structure with occasional glandular or Flexner rosette-like patterns and thick, solid, medullary-like or fascicular cords of spindle cells. These cords were separated by thin connective tissue septa (Fig. 1). Occasional palisading pattern was also asso- ciated with the tumor. These tumor cells had eosinophilic cytoplasm with pale, round to oval nuclei. Mitotic figures were frequently observed. Some areas of haemorrhage, necrosis, and infiltration of inflammatory cells were found. Histological examination revealed invasive growth of the tumor to the right nasal cavity and metastasis of the tumor tissue to the subparotid lymph node, in which the same his- tological features as those of the original tumor tissue were observed. Columnar cells consisting of the tubular or acinar structure showed strong cytokeratin immunoreactivity (Fig. 2a), while small round or spindle cells occasionally showed Fig. 3. Electron microscopy showing desmosome-like structures immunoreactivity for both NFP (Fig. 2b) and synaptophysin (arrows) between the tumor cells. Note no signs of dense-cored (Fig. 2c). A small population of the columnar cells were secretory granules in the tumor cells. × 14,000. positive for carnosine (Fig. 2d); positive findings were clearly shown in the normal olfactory cells in the intact olfactory epithelium of the dog. Ultrastructurally, the axons to the olfactory bulb; the sustentacular cells being the columnar type of the tumor cells was characterized by des- supportive element; and the basal cells having a potential of mosome-like structure between the tumor cells. Neither differentiation to either neurosensory cells or sustentacular dense-cored granules nor neuritic structure were observed in cells [6]. None of these cells normally contains neurosecre- the tumor cells (Fig. 3). A small number of microvilli-like tory granules. These olfactory structures are considered to structure were occasionally demonstrated in the luminal sur- be originated from the ectodermal placodes [13]. Ultra- face of the acinar structure. Compactly packed round to structurally, reported olfactory neuroblastomas in both spindle cells also showed similar ultrastructural findings humans and animals frequently contained neurosecretory with rare structure of tight junction. granules, leading researchers to believe that these tumors The olfactory epithelium is composed of three cell types: originated from regional neural crest tissue rather than from the neurosensory cells (olfactory cells) extending their the olfactory epithelium [6, 7]. Based on the findings from OLFACTORY NEUROEPITHELIOMA IN A DOG 393 immunohistochemistry and electron microscopy, Hassoun 2. Berger, L. and Coutrat, H. 1926. Bull. Assoc. Fr. Etude Cancer et al. [9] and Takahashi et al. [23] concluded that cases of 15: 404–414. the olfactory neuroblastomas contained a rare variant, olfac- 3. Berger, L., Luc, G. and Richard, D. 1924. Bull. Assoc. Fr. tory neuroepithelioma/esthesioneuroepithelioma, which Etude Cancer 13: 410–421. was a true neurosensorial tumor originating from the olfac- 4. Cantrell, R.W., Ghorayeb, B.Y. and Fitz-Hugh, G.S. 1977. Ann. Otol. Rhinol. Laryngol. 86: 760–765. tory epithelium and differed from reported so-called olfac- 5. Carlei, F., Polak, J.M., Ceccamea, A., Marangos, P.J., Dahl, tory neuroblastomas which were generally considered to be D., Cocchia, D., Michetti, F., Lezoche, E. and Speranza, V. “APUD tumors”. 1984. Virchows Arch. [A] 404: 313–324. Histological examination of the present tumor arising in 6. Chaundhry,