Chapter 40: Carotid Body Tumors and Vascular Anomalies

Carotid Body Tumors

Presentation and Natural History

• Also known as glomus caroticum.

• Benign neuroendocrine tumor arising from carotid body paraganglia.

• Normal function of carotid body is as a chemoreceptor for changes in blood oxygen, carbon dioxide, and hydrogen ion concentration.

• Two cell types:

  1. Chief cells (Type I)—neural crest derived and are the cells capable of releasing neurotransmitters

  2. Sustentacular cells (Type II)—supporting cells, similar to glia

• Arranged in “zellballen” (German for “balls of cells”) configuration, consisting of tumor nests surrounded by fibrovascular stroma.

• Most common paraganglioma of the head and neck (45%-60%).

• Sporadic

  1. Typically present in fifth and sixth decades

  2. Unusual in children

  3. No gender predilection

  4. Rarely bilateral (5%)

• Familial

  1. As many as 40% arise in patients with a hereditary predisposition.

  2. Most commonly related to mutations in one of the four subunits (A, B, C, D) of the succinate dehydrogenase complex genes, collectively referred to as SDHx.

  3. Screening for these mutations in all patients is now considered standard of care.

  4. Present at a younger age than sporadic cases.

  5. Less likely to be malignant.

  6. Increased incidence of bilaterality (30%) and other paraganglia tumors including pheochromocytoma.

• Hyperplastic

  1. Described in populations living at higher altitudes

  2. Though to be due to chronic hypoxia

  3. More commonly in women (may be related to anemia from menses)

• Physical examination

  1. Most common presentation is painless, enlarging neck mass (deep and high in the neck).

  2. Tethered vertically but mobile horizontally (Fontaine sign).

  3. May be pulsatile or have a bruit.

  4. Only 5% of the patients present with CN X or CN XII palsy.

• Slow growing and often overlooked for years by patients; the average tumor doubling time is 4 to 5.5 years.

• May encase carotid or invade artery and surrounding structures, especially nerves.

• Shamblin classification

  1. Type I—localized tumor, easily separated from the carotid.

  2. Type II—tumor is adherent to the vessels, or partially encases ECA or ICA.

  3. Type III—tumor completely encases at least one carotid artery (ICA or ECA).

  4. Predicts operative time, need for vascular repair, and risk of peripheral neurological deficits.

• Malignancy is rare (5%-10%)

  1. Pain is the most predictive feature, along with young age and rapid enlargement.

  2. No histologic criteria of malignancy for primary tumor.

  3. Malignancy is defined as the presence of regional or distant metastases; most importantly, local invasion or destructive behavior does not establish malignancy.

• Rarely functional (1%-3%)

  1. Routine laboratory evaluation of plasma or urine catecholamine metabolites should be included in the diagnostic workup to identify a secreting paragangliomas, or a concomitant pheochromocytoma.

  2. The best screening test is plasma-free metanephrines, second best is 24-hour urine fractionated metanephrines.

Diagnosis and Management

• Contrast enhanced computed tomography (CT) or magnetic resonance imaging (MRI):

  1. Best initial imaging study.

  2. Demonstrates relationship to carotid and can help differentiate between other potential tumors in that area (eg, schwannoma).

  3. Hypervascular mass typically splaying internal and external carotid.

     • If mass pushes both vessels anteromedially a vagal tumor should be considered.

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