Esthesioneuroblastoma. Intermediate filaments, neuroendocrine, and tissue-specific antigens

Proceedings of the 2023 North American Society of Head and Neck Pathology Companion Meeting, New Orleans, LA, March 12, 2023: Navigating New Developments in High Grade Sinonasal Neuroendocrine and Neuroectodermal Neoplasms

Although the definitions of sinonasal neuroendocrine and neuroectodermal neoplasms did not change substantially in the 5th edition WHO Classification of Head and Neck Tumours, the diagnosis of olfactory neuroblastoma (ONB), small cell neuroendocrine carcinoma, and large cell neuroendocrine carcinoma remains quite challenging in practice. Ambiguities surrounding the amount of keratin expression allowable in ONB and the amount of neuroendocrine differentiation seen in sinonasal undifferentiated carcinoma (SNUC) lead to significant diagnostic discrepancies at the high grade end of this tumor spectrum. Furthermore, a group of problematic neuroepithelial tumors that show overlapping features of ONB and neuroendocrine carcinoma have never been recognized in formal classification schemes. Since publication of the 5th edition WHO, two new tumor entities have been proposed that help resolve these problems. Olfactory carcinoma is defined by high grade keratin-positive neuroectodermal cells with frequent intermixed glands and shows recurrent Wnt pathway, ARID1A, and RUNX1 alterations. IDH2-mutant sinonasal carcinoma is a molecularly-defined category that encompasses tumors with undifferentiated (SNUC), large cell neuroendocrine, and neuroepithelial phenotypes. This review will provide a practical overview of these emerging entities and their application to diagnostic challenges in the post-WHO sinonasal neuroendocrine and neuroectodermal tumor classification.

Sinonasal Tumors With Neuroepithelial Differentiation (Olfactory Carcinoma): Delineation of Their Pathologic and Clinical Features With Insights into Their Relationship to Olfactory Neuroblastoma and Sinonasal Carcinoma

Olfactory carcinoma is one of many names applied to sinonasal malignancies with histologic similarity to olfactory neuroblastoma (ONB) but cytokeratin expression or gland formation. It is unclear whether these neuroepithelial tumors represent a unified category and if they are separate from ONB and currently-recognized sinonasal carcinomas. This study aims to explore their clinicopathologic characteristics based on a large collective experience. A total of 53 sinonasal tumors with neuroepithelial differentiation were identified affecting 41 men and 12 women, median age 47 years (range: 12 to 82 y). The vast majority arose in the superior nasal cavity and presented at the high Kadish-Morita stage. Frequent histologic findings included (1) lobulated and solid growth, (2) rosettes and/or neurofibrillary stroma, (3) high-grade cytology, (4) complex, often ciliated glands, (5) nonfocal pancytokeratin expression, (6) neuroendocrine pos+itivity, and (7) variable S100-positive sustentacular cells. Twelve patients with available follow-up (48%) developed progressive disease at a median 8 months (range: 0 to 114 mo to progression), and 7 (28%) died of disease. Despite disparate historical terminology, neuroepithelial differentiation is a recurrent and recognizable histologic pattern that is associated with aggressive behavior in sinonasal tumors. While tumors with this phenotype may originate from olfactory mucosa, well-developed epithelial features warrant separation from conventional ONB and neural elements distinguish them from most sinonasal carcinomas. Although their full histogenesis remains uncertain and some heterogeneity may exist, we propose that this pattern is sufficiently distinctive to merit separate recognition as olfactory carcinoma. Use of consistent nomenclature may facilitate greater recognition of tumors with this phenotype and understanding of their pathogenesis and classification.

Of mice and men: olfactory neuroblastoma among animals and humans

Olfactory neuroblastoma (ONB) is a rare tumour of nasal cavity and paranasal sinuses that arises from the olfactory neuroepithelium and has unpredictable clinical course. As the sense of smell is phylogenetically one of the first senses and olfactory neuroepithelium is evolutionary conserved with striking similarities among different species, we performed an extensive analysis of the literature in order to evaluate the similarities and differences between animals and humans on the clinical, morphological, immunohistochemical, ultrastructural and molecular level. Our analysis revealed that ONB was reported mainly in mammals and showed striking similarities to human ONB. These observations provide rationale for introduction of therapy modalities used in humans into the veterinary medicine. Animal models of neuroblastoma should be considered for the preclinical studies evaluating novel therapies for ONB.

Epizootic neoplasia of the lateral line system of lake trout (Salvelinus namaycush) in New York's Finger Lakes

This article documents an epizootic of inflammation and neoplasia selectively affecting the lateral line system of lake trout (Salvelinus namaycush) in 4 Finger Lakes in New York from 1985 to 1994. We studied more than 100 cases of this disease. Tumors occurred in 8% (5/64) of mature and 21% (3/14) of immature lake trout in the most severely affected lake. Lesions consisted of 1 or more neoplasm(s) in association with lymphocytic inflammation, multifocal erosions, and ulcerations of the epidermis along the lateral line. Lesions progressed from inflammatory to neoplastic, with 2-year-old lake trout showing locally extensive, intense lymphocytic infiltrates; 2- to 3-year-old fish having multiple, variably sized white masses up to 3 mm in diameter; and fish over 5 years old exhibiting 1 or more white, cerebriform masses greater than 1 cm in diameter. Histologic diagnoses of the tumors were predominantly spindle cell sarcomas or benign or malignant peripheral nerve sheath neoplasms, with fewer epitheliomas and carcinomas. Prevalence estimates did not vary significantly between sexes or season. The cause of this epizootic remains unclear. Tumor transmission trials, virus isolation procedures, and ultrastructural study of lesions failed to reveal evidence of a viral etiology. The Finger Lakes in which the disease occurred did not receive substantially more chemical pollution than unaffected lakes in the same chain during the epizootic, making an environmental carcinogen an unlikely primary cause of the epizootic. A hereditary component, however, may have contributed to this syndrome since only fish of the Seneca Lake strain were affected.

Alveolar rhabdomyosarcoma with neuroendocrine/neuronal differentiation: report of 3 cases

The aim of this study is to report the clinicopathologic characteristics of 3 cases of alveolar rhabdomyosarcoma with neuroendocrine/neuronal differentiation. Specimens of 3 cases of alveolar rhabdomyosarcoma were studied using histologic, immunohistochemical, ultrastructural, and molecular genetic techniques. The patients were a 19-year-old man with metastatic alveolar rhabdomyosarcoma in a groin lymph node, a 16-year-old girl with alveolar rhabdomyosarcoma of the perineum, and a 20-year-old man with recurrent orbital alveolar rhabdomyosarcoma. Microscopically, case 1 was composed of compact sheets of medium to large tumor cells. Cases 2 and 3 were small blue round cell tumors. Cases 1 and 3 were solid throughout, whereas case 2 demonstrated alveolar and solid architecture. By immunohistochemistry, the following markers were positive: desmin (3/3), myogenin (3/3), synaptophysin (3/3), and chromogranin (2/3). Ultrastructurally, sarcomeric filaments were seen in all cases, while neuroendocrine granules were detected only in case 1. PAX:FKHR fusion transcript was identified in case 2, case 3 had a variant PAX3 transcript, and case 1 was negative. The data presented expands the known differentiation of alveolar rhabdomyosarcoma.

Intra-epithelial neuroendocrine carcinoma of the nasal cavity

We describe a distinctive neuroendocrine carcinoma (NEC) that proliferated intra-epithelially. The tumor was 35 mm in diameter and arose from the right superior turbinate of a 46-year-old woman. Histologically, the tumor exhibited papillary growth and the tumor cells were localized in the thickened mucosal epithelium. The tumor cells had round to oval and vesicular or hyperchromatic nuclei, and cohered without any specific structure such as a fibrillary background, rosette or glandular structure. No stromal invasion by the tumor was observed. Immunohistochemically, the tumor cells were positive for neuron-specific enolase focally. In addition, many tumor cells expressed cytokeratin (AE1/AE3 and CAM 5.2), mostly with characteristic perinuclear dot-like patterns. Electron microscopy revealed focal but well-eveloped cytoplasmic processes containing arrays of microtubules and a few dense core granules. The tumor was considered to be a poorly differentiated neuroendocrine carcinomas (NEC) that exhibited exceptional intra-epithelial proliferation. The tumor completely disappeared after the stereotactic radiosurgery and has not recurred for 40 months. It might be difficult to distinguish a poorly differentiated NEC in the sinonasal region from other neuroectodermal tumors, including olfactory neuroblastoma, but the differential diagnosis is important because each tumor has different clinicopathological characteristics.

Neuroectodermal neoplasms of the head and neck with emphasis on neuroendocrine carcinomas

Tumors exhibiting neuroectodermal differentiation occur throughout the body, and the diverse tissues of the head and neck give rise to a wide assortment of these neoplasms. Neuroectodermal neoplasms may be divided into lesions showing primarily epithelial differentiation (Group I, neuroendocrine carcinomas) and a more diverse group (Group II) of nonepithelial neoplasms. This article reviews these neuroectodermal tumors of the head and neck with emphasis on the neuroendocrine carcinomas and their nomenclature. The author believes that with regard to Group I tumors, the older terminology of carcinoid, atypical carcinoid, and small cell carcinoma should be replaced by subclassifications of well-differentiated, moderately differentiated, and poorly differentiated neuroendocrine carcinoma. The latter category should be further subdivided into small cell and large cell variants. Neuroendocrine carcinomas, particularly the moderately differentiated subtype, are often underdiagnosed in the head and neck region. In the larynx, these tumors are the most common form of nonsquamous carcinoma. Poorly differentiated neuroendocrine carcinoma of small cell type is most common in the salivary glands but can occur elsewhere in the region. The large cell subtype of poorly differentiated neuroendocrine carcinoma has not been well documented in this region. However, the most likely candidate for this tumor category is the so-called sinonasal undifferentiated carcinoma. Group II tumors discussed include olfactory neuroblastoma, malignant melanoma, and Ewing's sarcoma. In addition, differential diagnostic problems related to Group I and II tumors are reviewed in detail. This article reviews and updates our understanding of neuroectodermal neoplasms arising in the head and neck. The focus is on tumors that exclusively involve this region or show a strong predilection to occur here.

Esthesioneuroblastoma: a meta-analysis and review

Our objective was to review recent developments in diagnosis, staging, and treatment of esthesioneuroblastoma (ENB). A meta-analysis of publications between 1990 and 2000 was carried out, and studies were classified according to their main subject: origin/aetiology of ENB, histopathological diagnosis, and treatment. Data so far point to the basal progenitor cells of the olfactory epithelium as the origin of ENB. Histopathological diagnosis remains difficult and is based on results of antigen expression detected through a panel of antibodies by immunohistochemistry. RT-PCR of HASH expression could be a specific marker of ENB. Overall and disease-free survival at 5 years averaged 45% (SD 22) and 41% (SD 21) in the studies included in the meta-analysis. Survival in Hyams' grades I-II was 56% (SD 20) compared with 25% (SD 20) in grades III-IV (odds ratio 6.2). In patients with metastases in cervical lymph nodes (on average 5% of the total) survival was 29%, compared with 64% for patients with N0 disease (odds ratio 5.1). Survival according to treatment modalities was 65% for surgery plus radiotherapy, 51% for radiotherapy and chemotherapy, 48% for surgery, 47% for surgery plus radiotherapy and chemotherapy, and 37% for radiotherapy alone. The histopathological grading according to Hyams and the presence of cervical lymph-node metastases emerged as prognostic factors. A combination of surgery and radiotherapy seems to be the optimum approach to treatment. The exact role of chemotherapy in treatment protocols is still unclear. The role of elective neck dissection is unclear.

Usefulness of electron microscopy in the diagnosis of "small" round cell tumors of the sinonasal region

The sinonasal region is known to harbor several types of tumors that belong to the general category of "small" round cell tumors and offer considerable diagnostic challenges. This study evaluated 33 cases of such tumors by electron microscopy to characterize their ultrastructural features in conjunction with immunohistochemistry, in an attempt to define diagnostic criteria of various types. Electron microscopy was useful in the proper classification of tumors in 27 cases: esthesioneuroblastoma (EN), 12; undifferentiated carcinoma, 6; melanoma, 3; lymphoma, 3; melanotic neuroectodermal tumor, 1; rhabdomyosarcoma, 1; and pituitary adenoma, 1. In the remaining six cases, the ultrastructural features were those of poorly differentiated carcinomas. They usually exhibited some epithelial characteristics as well as neuroendocrine features by immunohistochemistry and electron microscopy. These tumors could be best described as poorly differentiated neuro-endocrine carcinomas (malignant neuroepitheliomas). The most controversial diagnostic problems existed between the tumors categorized as esthesioneuroblastomas and neuroendocrine (NE) carcinomas. Esthesioneuroblastomas were characterized by uniform round nucleated cells with variable amounts of dendritic processes containing numerous dense core granules ranging from 150 to 350 nm in the perikarya and dendritic processes. Dendritic processes contained longitudinally arranged neural tubules and revealed an occasional synaptic junction. In three of the 12 cases of EN, cells with the appearance of sustentacular cells were recognized by electron microscopy. The NE carcinomas usually consisted of closely packed round cells with scanty cytoplasm that lacked any feature of neuroblastic cells. The tumor cells in this category often were epithelioid in appearance and exhibited a varying degree of cytokeratin positivity. Neuron-specific enolase was also positive in all cases, further suggesting their neuroepithelial nature. The greatest difference between EN and NE carcinomas was the absence of sustentacular cells in NE carcinomas. Immunohistochemical and electron microscopic studies are essential in the differential diagnosis of EN and NE carcinomas, because their microscopic appearance is very similar. The study indicates that EM is useful in the diagnostic categorization of sinonasal tumors of uncertain nature, particularly when it is used in conjunction with immunohistochemistry.

Olfactory neuroblastoma. An immunohistochemical, ultrastructural, and flow cytometric study

BACKGROUND

Olfactory neuroblastoma is an uncommon neuroectodermal tumor of the upper nasal cavity, microscopic features of which are not always homogeneous. No morphologic features have been found to correlate reliably with prognosis.

METHODS

Twenty-six olfactory neuroblastomas occurring in 14 females and 12 males, ages 18-78 years, were studied by immunohistochemistry, electron microscopy, and DNA flow cytometry. Survival rates were statistically analyzed relative to several variables.

RESULTS

Microscopically, 22 tumors formed a morphologic spectrum intermediate between paraganglioma (PG) and neuroblastoma (NB). Others included two ganglioneuroblastomas (GNB), one lesion exhibited biphasic (neuronal and epithelial) differentiation, and one tumor showed predominantly epithelial features. Immunoreactivity for neuronal and neuroendocrine markers included synaptophysin in 77%, neurofilament protein in 38%, class III beta-tubulin in 81%, and chromogranin A in 77%. In 88% of cases, elongated S-100 protein-positive cells surrounded tumor lobules. Cytokeratin and epithelial membrane antigen immunoreactivity were noted in six (23%) and two (8%) tumors, respectively. Aberrant p53 expression was detected in 16 tumors (62%). The Ki-67 labeling index (LI) varied from 0%-43.8% (mean, 7.4%). Ultrastructurally, 80-230 nm dense core granules were noted within perikarya and as in microtubule-containing processes in all of the 11 tumors studied by electromicroscopy. Lobules of seven tumors were surrounded by electron-dense sustentacular cells. Epithelial tumors exhibited obviously epithelial features in addition to neuronal differentiation. DNA flow cytometry demonstrated a high incidence of polyploidy and aneuploidy (78%) and a wide range of percent S phase fractions (1.5%-21.8%; mean, 9.0%). The study showed that longer survival rates are related significantly to (1) the occurrence of metastases which was linked to tumor subtype, (2) to a higher incidence of S-100 protein-positive cells, and (3) to a low (< 10%) Ki-67 labeling index.

CONCLUSIONS

The present study indicates that (1) although typical olfactory neuroblastomas exhibit PG/NB differentiation, they more closely resemble PG, (2) occasional tumors show GNB and/or epithelial differentiation, and (3) survival rates may correlate with S-100 protein immunoreactivity and Ki-67 LI. Cancer 1995; 76:4-19.

Neuroblastoma of parotid gland: report of a case and immunohistochemical characteristics

A case of a parotid mass in a 2-year-old boy, postoperatively diagnosed as neuroblastoma, a rare tumour not previously reported in the parotid gland is presented. The neoplasm developed within the parotid gland as a painless mass without regional lymphadenopathy. Histopathologically, the tumour showed primitive nerve cells-neuroblasts-with round or oval dark basophilic nuclei and scanty cytoplasm. The cells were arranged in circular rosettes around an eosinophilic mass consisting of very fine filaments originating in the tumour cells or papillary configuration and sometimes scattered in the poorly developed stroma. Immunohistochemical evaluation of the tumour showed a positive immunoreactivity for vimentin, alpha and beta subunits of S-100 protein, neurone-specific enolase (NSE), substance P, met-enkephalin and chromogranin but cytokeratins, desmin, actin, myosin, glial fibrillary acidic protein (GFAP) and calcitonin gene related peptide (CGRP) were negative. The histopathological and immunohistochemical findings conclude a diagnosis of neuroblastoma of the parotid gland.

Cushing's syndrome secondary to olfactory neuroblastoma

A case of olfactory neuroblastoma in a 36-year-old woman who presented with florid Cushing's syndrome is reported. A nasal polyp, which proved to be an olfactory neuroblastoma, was resected. The procedure was followed by complete remission from the endocrinologic abnormalities. Postoperatively, the patient was well for 5 years until recurrence of both Cushing's syndrome and the nasal polyp was noted. Following combined transnasal-transcranial resection of the tumor, which extended into the anterior cranial fossa, the patient again experienced complete remission of Cushing's syndrome. Immunohistochemistry showed the tumor to be positive for neuron-specific enolase, synaptophysin, chromogranin, adrenocorticotropic hormone, beta-endorphin, and S-100 protein. Electron microscopy revealed neuritic processes containing microtubules and neurosecretory granules. This is the first reported case of Cushing's syndrome secondary to olfactory neuroblastoma.

The biology and pathology of selected skull base tumors

This paper describes the pathobiology of some of the more common skull base tumors. In addition to clinicopathologic features, emphasis is placed upon methods of diagnosis utilizing immunoperoxidase stains and molecular markers that may or may not impact upon prognosis.

Electron microscopic and immunohistochemical findings in a case of olfactory neuroblastoma

A case of olfactory neuroblastoma is reported. Light microscopic examination showed various arrangements of poorly differentiated tumour cells forming either uniform sheets or convoluted cords of multiple cell layers orientated toward a richly vascular stroma. Electron microscopic examination showed the presence of abundant cytoplasmic filaments and processes, and dense core endocrine vesicles ranging from 100-160 nm in diameter in both the perinuclear region and tumour cell processes. Immunohistochemical staining was positive in most of the tumour cells for neuron specific enolase, and in a few cells for S-100 protein, vimentin, and serotonin, but staining for desmin and keratin produced no reaction.

Sinonasal primitive neuroectodermal tumor arising in a long-term survivor of heritable unilateral retinoblastoma

BACKGROUND

Patients who survive retinoblastoma (RB) are at risk for having second nonocular tumors, usually osteosarcomas, which often are fatal. Such patients almost always have bilateral RB.

METHODS

This article reports a woman who, at the age of 1 year had been cured of a unilateral RB by radiation therapy and enucleation. Eighteen years later, she had a sinonasal small cell tumor that rapidly recurred and proved fatal 2 months after surgical debulking. The tumor was studied by immunohistochemistry and electron microscopic (EM) examination.

RESULTS

It showed diffuse neuron-specific enolase staining, focal weak staining for chromogranin, synaptophysin, and Leu-7 monoclonal antibodies in paraffin-embedded, B5-fixed tissue (Great Lakes Diagnostics, Troy, MI). EM study showed an undifferentiated primitive neuroectodermal tumor with many polyribosomes, simple cell junctions, few microtubules, and rare dense core granules.

CONCLUSIONS

The combined immunohistochemical, ultrastructural, and clinical features of the tumor were interpreted as a sinonasal primitive neuroectodermal tumor with early neuronal differentiation. The tumor was pathologically indistinguishable from poorly differentiated olfactory neuroblastoma (ONB) and Ewing sarcoma.

Intracranial olfactory neuroblastoma: evidence for olfactory epithelial origin

AIMS

To determine the possible histogenesis of the intracranial variant of olfactory neuroblastoma.

METHODS

Four specimens from three cases of intracranial olfactory neuroblastoma were studied by light microscopy and immuno-histochemistry, and electron microscopy in two cases.

RESULTS

Light microscopical examination showed small cell tumour with additional features of epithelioid cells in one case and ganglion cells in another. Olfactory and Homer-Wright rosettes were present. All the specimens showed a uniform positive reaction to neurone specific enolase, S-100, and cytokeratin antibodies. Glial fibrillary acidic protein was absent. The salient electron microscopic features were the presence of cell junctions, cytoplasmic intermediate filaments, basal bodies and cytolasmic processes. Dense cored vesicles were absent.

CONCLUSIONS

The results strongly support the view that intracranial olfactory neuroblastomas are of olfactory epithelial origin and differ from conventional neuroblastomas.

Neuroendocrine tumors of the nasal cavity: an ultrastructural and morphometric study of 24 cases

A series of 24 small cell nasal tumors with neuroendocrine differentiation was studied by electron microscopy, and the numbers of secretory granules and cell junctions were assessed. To investigate the relationship between the extent of dendrite formation and the behavior of the tumors, the size of the tumor cells and the area occupied by dendritic processes were determined for each tumor by morphometric analysis performed on low-magnification electron micrographs. A positive correlation was demonstrated between the dendritic area index and the survival of the patients (P = 0.017). Neither the number of secretory granules nor the frequency of cell junctions was prognostically significant.

Pneumocephalus following treatment of esthesioneuroblastoma

The course of a patient with an olfactory neuroblastoma treated with conventional doses of chemotherapeutic agents and radiotherapy is presented. The patient survived 34 months after tumour necrosis with resultant pneumocephalus requiring surgical intervention.

Olfactory neuroblastoma

Fifteen patients with olfactory neuroblastoma were treated during the 17-year period of 1969 to 1986. Data was analyzed with respect to age at presentation, sex, presenting signs and symptoms, stage, and results of treatment. Age ranged from 4 to 67 years with the median age being 27 years. Median follow-up was 8 years. Local control was achieved in nine of nine patients or 100% with successful surgical resection, i.e., minimal residual disease, followed by postoperative radiation therapy (45 to 65 Gy) was employed. There were no distant failures when the primary site was controlled. Regional lymph node metastases were infrequent: only 13% (two of 15 patients) presented with positive nodes. Three of four patients treated initially with surgery alone had a local recurrence, two of which were successfully salvaged by combined therapy. There were four patients treated with radiation therapy alone: three had persistent disease after radiation therapy, and one patient was controlled with 65 Gy. Olfactory neuroblastoma has a propensity to recur locally when treated with surgery alone. The authors' experience suggests excellent local control can be achieved with surgery immediately followed by radiation therapy. Thus the authors recommend planned combined treatment for all resectable lesions.

Pigmented esthesioneuroblastoma showing dual differentiation following transplantation in nude mice. An immunohistochemical, electron microscopical, and cytogenetic analysis

Esthesioneuroblastoma (ESTH) is a neuroepithelial-cell-derived neoplasm of the olfactory mucosa composed of homogeneous small round cells which contain neurosecretory granules. Melanin has been detected in such tumours only occasionally. Here we describe a new case of ESTH with divergent differentiation. The primary neoplasm was found in a 67 year-old female, involving the left nasal and maxillary sinus; she died of cerebral metastasis ten months after diagnosis. Histologically only small round cells were seen, with S-100 and NSE positivity. Electron microscopy revealed neurosecretory granules and filaments, as well as the occasional presence of melanosomes. A nude mice xenograft line has been established, and is presently in its ninth transfer. Two cell types are present: small round-to-spindle shaped cells with neural features, and large epithelial-like ones. Both immunohistochemistry and electron microscopy confirm this dual differentiation, with the presence of membrane-bound dense-core neural secretion, as well as melanosomes of neuroectodermal origin. Additionally, an in vitro cell line has been established. Cytogenetic analysis confirmed the presence of both malignant human melanoma patterns; non-random abnormalities in chromosomes 1 and 6, extra copies of chromosome 7. Duplication of the long arm of chromosome 14, as seen in olfactory neuroblastoma, is also seen.

Esthesioneuroblastoma: a nasal catecholamine-producing tumor of neural crest origin. Demonstration of tyrosine hydroxylase-immunoreactive tumor cells

An esthesioneuroblastoma in a 16-year-old male was studied ultrastructurally and immunohistochemically, using antiserum against tyrosine hydroxylase (TH), a rate-limiting enzyme in the catecholamine-synthesizing pathway. Tumor cells were fairly uniform in appearance, showing scanty eosinophilic cytoplasm and round to oval hyperchromatic nuclei, and were arranged in nests and cords of various sizes. Ultrastructurally, individual tumor cells had well-developed cell organelles including polyribosomes, microtubules, intermediate filaments, centrioles, Golgi apparatus and mitochondria. Secretory-like granules were occasionally found, predominantly in the cell processes. Immunohistochemically, many tumor cells were shown to be immunoreactive for TH. This finding strongly suggested that the present tumor was capable of producing catecholamines and that it might be derived from certain sympathetic neuronal cell nests in the superior nasal cavity.