Chemodectoma

Paragangliomas are neuroendocrine tumors arising from extra-adrenal autonomic ganglia. We present what is to our knowledge the first immunohistochemically documented case of a paraganglioma of the tongue, a 2.5-cm benign tumor growing in the position of the foramen cecum. The patient was an elderly woman who presented with throat irritation. The histologic profile and ultrastructural appearance of this lesion were classic for paraganglioma, and cells stained strongly for neurosecretory granules by immunohistochemistry. Carcinoid, ectopic thyroid neoplasm, and other tumors that mimic paraganglioma were ruled out on immunohistochemical grounds. To our knowledge, paraganglia have not been previously documented in the tongue; this tumor may have arisen from a branch of cranial nerve VII or IX, or from an embryologic remnant of the thyroid or thyroid capsule.

(Arch Pathol Lab Med. 2000;124:877-879)

Paragangliomas are neuroendocrine tumors similar to pheochromocytomas, but arising from extra-adrenal autonomic ganglia.1,2 Immunohistochemical techniques are necessary to make a definitive diagnosis of paraganglioma, as their characteristic microscopic Zellballen appearance can occasionally be mimicked by other neoplasms.

Head and neck paraganglia occur in association with the carotid body, the ganglion nodosum of the vagus nerve, the middle ear (jugulotympanic paraganglia), and in other rarer sites where paraganglia are known to exist.2 To our knowledge, paraganglia have not been discovered previously in the tongue. We describe the first immunohistochemically documented case of a paraganglioma arising in the tongue and discuss its possible histogenesis.

REPORT OF A CASE

The patient, a French-Canadian woman, first presented in 1990 at the age of 72 years with a complaint of throat irritation. She was a heavy smoker and had been diagnosed with clinical hypothyroidism in 1988. Indirect laryngoscopy revealed a 1-cm mass at the base of the tongue, in the midline just posterior to the foramen cecum. Radioiodine scan demonstrated a normally located thyroid with multinodular goiter, or Hashimoto thyroiditis, and no lingual thyroid tissue. An incisional biopsy of the tongue mass was performed in May 1990. Microscopic and immunohistochemical analysis permitted the diagnosis of benign paraganglioma. Although surgical excision was planned, the patient did not return for the procedure.

She presented again in January 1997 with recurrent chronic throat irritation. On clinical examination, a small granulating mass was seen at the back of the tongue. Suspension microscopic laryngoscopy revealed that the visible small mass was situated on top of a 2.5-cm sessile hard tumor at the base of the tongue. Computed tomographic scan of the neck (Figure 1) showed a 1.6 x 2.5-cm solid mass, exactly in the midline. An incisional biopsy was performed, again showing paraganglioma. Clinical investigation of urine was negative for catecholamines. The patient refused a recommended complete excision of the tumor.

MATERIALS AND METHODS

Biopsy fragments were fixed in 10% buffered formalin for histology and immunohistochemistry, and in 3% glutaraldehyde for electron microscopy. Histochemical stains included hematoxylineosin, periodic acid-Schiff, Gomori stain for reticulin, Masson-- Fontana stain for argentaffin granules, and Pascual's modification of the Grimelius stain for argyrophil granules. Immunohistochemistry was performed on paraffin sections using the avidinbiotin technique and 3,3'-diaminobenzidene as a substrate. Appropriate positive controls and negative controls with the deletion of the primary antibody were included. Antibodies used included calcitonin, chromogranin A, neuron-specific enolase, S100, and high-molecular-weight cytokeratins (all from Dako Diagnostics Canada, Inc, Mississauga, Ontario, Canada) and low-molecular-weight cytokeratins (Becton Dickinson Immunocytometry Systems, San Jose, Calif).

PATHOLOGIC FINDINGS

The pathologic findings of both biopsies were identical. Biopsy fragments were 3 mm in diameter, and the tissue was grossly homogeneous and highly vascular.

Light microscopy (Figure 2, A) revealed growth in a submucosal location of the tongue. The lesion was composed of round nests of uniform polygonal chief cells with extensive granular eosinophilic cytoplasm. The nuclei of these neoplastic cells were large, regular, and centrally located, and showed occasional vesiculation. There were no mitoses. Nests of polygonal chief cells were separated by the cytoplasmic processes of elongated sustentacular cells, and there was an associated fibrovascular stroma. There was no significant gland formation, anaplasia, necrosis, mitotic activity, or invasion in the biopsy specimens.

Immunohistochemical and other special staining techniques supported the diagnosis of paraganglioma and ruled out other tumors in the pathologic differential diagnosis (Table). Electron microscopy (Figure 2, B) revealed a chief cell ultrastructure that was highlighted both by large numbers of mitochondria and, particularly, by numerous 100- to 200-nm, uniform neurosecretory granules, consistent with previous descriptions of paraganglioma ultrastructure.2

COMMENT

As Lack2 stated, paragangliomas "can present in unusual anatomic locations where normal paraganglia are not well documented." Certainly, a paraganglioma does not enter into the usual differential diagnosis for a mass at the base of the tongue, which includes not only squamous cell carcinoma, but also such entities as lingual tonsil, lingual thyroid, salivary gland tumor, benign nerve sheath tumor, granular cell tumor, leiomyoma, and osseous choristoma.3 While such lesions are easily excluded by routine morphologic analysis, a nested Zellballen architecture, as seen in this case, is not specific for paragangliomas and can be present in glomus tumors of the peripheral vasculature, melanoma, "paraganglioid" carcinoid tumors, hyalinizing trabecular ("paraganglioma-like") thyroid adenoma, medullary thyroid carcinoma, and alveolar soft part sarcoma.2,4 Grimelius and chromogranin A stains confirm the neurosecretory nature of the chief cell granuels, and togehter with neuron-specific enolase establish that the tumor arises from a neuroendocrine cell lineage, rather then a modified muscle cell type. The membrane-bound gridded crystal ultrastructure characteristic of alvelor soft part sarcoma was not present in this case. Masson-Fontana (argentaffin) stain was negative, as is usual for paragangliomas; in this respect paragangliomas differ from other neural crest tumors, such as melanoma, which retain greater quantities of bioactive amines. Staining for S100 protein was confined to the sustentacular cells in this case and did not stain the nested chief cells themselves. Tumor cells were significantly negative fro cytokeratins, thyroglobulin, amyloid, and calcitonin, arguing against carcinoid, hylinizing trabecular adenoma of the thyroid, or medullary thyroid carcinoma. Indeed, medullary carcinoma does not arise from lingual thyroids, owing to the different embroyologic origin of thyroid C cells.

The vast majority of head and neck paragangliomas arise from the carorid body, ganglion nodosum, jugoulotympanic paraganglia, or the superior and inferior laryngeal nerves. Cases of orbital, nasopharyngeal, and thyroid paragangliomas have been characterized.2 Anatomic locations of minor paraganglia are not always well known, and it is possible that finding a paraganglioma at the base of the tongue implies the presence of paraganglia related to the glossopharyngeal nerve or the chorda tympani branch of the facial nerve. Parasympathetic fibers from these cranial nerves synpase in the otic and submandibular ganglia, respectively, whereas the midling locatio of this tumor at the site of the foramen cecum provokes consideration of a relation to the thyroglossal duct. Paraganglia have been indentified in the thyroid capsule,5 but not within the parenchyma of the thyroid gland. Nevertheless, benign thyroid paragangliomas, originating in some cases from the gland parenchyma, can arise independently of known laryngeal nerve paraganglia.6 Reports of thyroid paragangliomas are rare,2,6 as are reports of carcinomas arising from lingual thyroid or thyroglossal tract tissue,7,8 so this event would have to be extraordinarily unusual.

The Intalian literature contians the only reported case of a tongue "paraganglioma".9 This article described a "chemodectoma or non-chromaffin paraganglioma," which presented as a tender vascular mass on the leteral tongue of 34-year-old man. The article was published in 1970, and the authors made no electron microscopic or immunohistochemical characterization of the tumor. Unfortunately, the title represents use of an older, ambiguous terminology, and in fact the report appears to describe a glomus tumor of the peripheral vasculature, which can occasionally present in the oral cavity.10 Consequently, we believe the case we report here represents the first description of a true paraganglioma arising in the tongue.

Malignancy is difficult to predict using histologic criteria. Only an estimated 10% of paragangliomas are malignant, and this proportion may be even smaller in the head and neck region.2 The slow growth, radiologic circumscription, presence of S100-positive sustentacular cells, and well-differentiated histologic appearance of the tongue paraganglioma reported here suggest it will also behave as a benign tumor.

Dr Nielsen was supported by the McGill MD/PhD program (Montreal, Quebec, Canada) and by a Medical Student Fellowship in Pathology from the American Society of Clinical Pathologists (Chicago, Ill). We thank Sue Ballarano for assisting in the translation of Italian references.

References

1. Kliewer KE, Cochran AJ. A review of the histology, ultrastructure, immunohistology, and molecular biology of extra-adrenal paragangliomas. Arch Pathol Lab Med. 1989;113:1209-1218.

2. Lack EE. Pathology of Adrenal and Extra-Adrenal Paraganglia. Philadelphia, Pa: WB Saunders; 1994.

3. Moore K, Worthington P, Campbell RL. Firm mass of the tongue. I Oral Maxillofac Surg. 1990;48:1206-12 10.

4. Collina G, Maiorana A, Fano RA, Cesinaro AM, Trentini GP. Medullary carcinoma of the thyroid gland with sustentacular cell-like cells in a patient with multiple endocrine neoplasia, type IIA: report of a case with ultrastructural and immunohistochemical studies. Arch Pathol Lab Med. 1994;118:1041-1044.

5. Zak FG, Lawson W. Glomic (paragangliomic) tissue in the larynx and capsule of the thyroid gland. Mt Sinai j Med. 1972;39:82-90.

6. LaGuette J, Matias-Guiu X, Rosai J. Thyroid paraganglioma: a clinicopathologic and immunohistochemical study of three cases. Am I Surg Pathol. 1997; 21:748-753.

7. Zink A, Raue F, Hoffman R, Ziegler R. Papillary carcinoma in an ectopic thyroid. Hormone Res. 1991;35:86-88.

8. Lustmann J, Benoliel R, Zeltser R. Squamous cell carcinoma arising in a thyroglossal duct cyst in the tongue. J Oral Maxillofac Surg. 1989;47:81-85.

9. Scopelliti G, Camera A, Barbato U. Chemodectoma della lingua: criteri diagnostico-differenziali ed istogenetici. Ann Stomatol. 1970;19:819-834.

10. Geraghty JM, Thomas RWN, Robertson JM, Blundell JW. Glomus tumour of the palate: case report and review of the literature. Brj Oral Maxillofac Surg. 1992;30:398-400.

Accepted for publication November 12, 1999.

From the Department of Pathology, Vancouver Hospital & Health Sciences Centre and the University of British Columbia, Vancouver, Canada (Dr Nielsen); and the Departments of Otolaryngology (Dr Sejean) and Pathology (Dr Onerheim), St Mary's Hospital and McGill University, Montreal, Quebec, Canada.

Reprints: Ronald Onerheim, MD, Department of Pathology, St Mary's Hospital Center, 3830 Ave Lacombe, Montreal, Quebec, Canada H3T 1M5.

Copyright College of American Pathologists Jun 2000
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