Carotid body tumor (paraganglioma).

Of all the paragangliomas in the head and neck, carotid body tumors are the most common. They arise from the chemoreceptor organ (paraganglion) located in the adventitia of the carotid artery bifurcation. They preferentially affect women who live at high altitudes, and they are most likely to occur during the fifth decade of life. Familial cases, such as multiple endocrine neoplasia syndromes, tend to develop in younger patients, and they are more frequently bilateral and multifocal.

Carotid body tumors typically present as painless neck masses just lateral to the tip of the hyoid bone. Larger neoplasms may manifest as hypopharyngeal masses associated with hoarseness. These tumors usually cause a lateral displacement and widening of the carotid 'artery bifurcation that is best demonstrated on radiographic imaging studies.

These tumors measure approximately 4.0 cm in their greatest dimension, and they often lack a capsule. Microscopically, they are made up of paraganglial cells organized into nests known as Zellballen (literal German translation: cellballs). These nests are supported by a sustentacular-cell framework. A rich vascular network invests the tumor cell nests (figure 1, A). Tumor cells can be polygonal, oval, or spindle-shaped, and they contain variable amounts of granular, slightly basophilic cytoplasm. Nuclear anaplasia can be seen, but mitotic figures are rare. Tumor degeneration can be seen in masses that have undergone preoperative embolization to facilitate surgical removal and reduce blood loss (figure 1, B).

[FIGURE 1 OMITTED]

The chief cells are strongly and diffusely immunoreactive with chromogranin and synaptophysin, while the supporting sustentacular cells react with S-100 protein (figure 2). Carotid body tumors must be differentiated histologically from other similar-appearing neoplasms, including medullary thyroid carcinomas, laryngeal neuroendocrine neoplasms, and metastatic carcinomas, particularly renal cell carcinomas.

[FIGURE 2 OMITTED]

Most paragangliomas are benign neoplasms; approximately 5 to 10% behave in a malignant fashion. Further, approximately 10 to 15 % of carotid body tumors recur. Histologic features alone do not correlate well with malignant behavior, although extensive local invasion and metastatic disease can be used to define malignant neoplasms. Common metastatic sites include the regional lymph nodes, liver, bone, and lung. Surgical removal is the treatment of choice and is generally facilitated by preoperative embolization. Radiation therapy is palliative and is best reserved for unresectable and multifocal tumors.

Suggested reading

Lack EE, Cubilla AL, Woodruff JM. Paragangliomas of the head and neck region. A pathologic study of tumors from 71 patients. Hum Pathol 1979;10:191-218.

Muhm M, Poltcrauer R Gstottner W, et al. Diagnostic and therapeutic approaches to carotid body tumors. Review of 24 patients. Arch Surg 1997;132:279 84.

From the Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston.