RESIDENT CASE STUDIES

Week 10 June 23 - June 27, 2003: Case 2   

Table of Contents | List of Diagnoses | Case 1 | Case 2 | Case 3

48 year old caucasian female with a history of dizziness, blackouts, and left arm numbness 

Discussion
The carotid body (CB) is a highly specialized small organ located at the bifurcation of the common carotid artery in the neck and plays an important role in acute adaptation to hypoxia. The CB is the most common tumor site in head and neck paragangliomas.¹ 

Carotid body tumor (CBT) is rare, mostly slow-growing and benign. It arises from paraganglionic tissue at the bifurcation of the common carotid artery, usually arising in the 6^th decade of life. It rarely exceeds 6 cm in diameter. It commonly occurs singly and sporadically, but may be familial with autosomal dominant transmission in the multiple endocrine neoplasia II syndrome. Frequently, and in this case, there are multiple tumors. Sometimes they are bilaterally symmetric.^2,4 CBTs can cause significant morbidity because of their proximity to major arteries and nerves in the head and neck.¹ Carotid body tumors frequently recur after incomplete resection, and despite their benign appearance, many metastasize to local and distant sites.⁴ Unfortunately, it is almost impossible histologically to judge the clinical course of a carotid body tumor--mitoses, pleomorphism, and even vascular invasion are unreliable.⁵ 

The carotid body tumor is a prototype of a parasympathetic paraganglioma. The microscopic features of all paragangliomas, wherever they arise, are remarkably uniform. They are composed of nests (zellballen) of polygonal chief cells enclosed by trabeculae of fibrous and sustentacular elongated cells. The tumor cells have abundant, clear or granular, eosinophilic cytoplasm and uniform, round to ovoid, sometimes vesicular nuclei. The salt and pepper appearance of the nuclei of neuroendocrine tumors is readily apparent. In most tumors, there is little cell pleomorphism, and mitoses are scant.

Electron microscopy often discloses well-demarcated neuroendocrine granules in paravertebral tumors, but they tend to be scant in nonfunctioning tumors. However, the cells in most tumors are argyrophilic and stain positively for neuroendocrine markers by immunohistochemistry.⁵ Substentacular cells may show positive reactivity with S100. 

Resection of carotid body tumors (neck paragangliomas) carries inherent risks of injury to the cranial nerves and other structures as well excessive blood loss.³ 

References:

¹Baysal BE, Myers EN. Etiopathogenesis and clinical presentation of carotid body tumors. Microsc Res Tech. 2002 Nov 1;59(3):256-61.

²Lord RS, Chambers AJ. Familial carotid body paragangliomas and sensorineural hearing-loss: a new syndrome. Cardiovasc Surg. 1999 Jan;7(1):134-8.

³Kafie FE, Freischlag JA. Carotid body tumors: the role of preoperative embolization. Ann Vasc Surg. 2001 Mar;15(2):237-42. Epub 2001 Mar 01.

⁴Cotran: Robbins Pathologic Basis of Disease, 6th ed. 1999 W. B. Saunders Company.

⁵Wick MR, Rosai JR: Neuroendocrine tumors of the mediastinum. Semin Diagn Pathol 8:35, 1991.