Carotid body tumor, also known as a chemodectoma or carotid body paraganglioma, is a highly vascular glomus tumor that arises from the paraganglion cells of the carotid body. It is located at the carotid bifurcation with characteristic splaying of the ICA and ECA.
Typically, carotid body tumors are diagnosed in the 4th to 5th decades, and have a female predilection like the other paragangliomas of the head and neck 1,3. They are the most common type of paraganglioma of the head and neck (account for 60-70%). In approximately 10% of cases, they are bilateral 1,3.
A small number are familial (7-10%), and in such cases, they are frequently multicentric (35-50%) 1,3. When familial, they are usually autosomal dominant in inheritance, and associated with 3:
- multiple endocrine neoplasia: MEN IIa and MEN IIb
- Carney triad
Clinical presentation is usually with a slow growing rounded neck mass. It is usually located anterior to the sternocleidomastoid near the angle of the mandible at the level of the hyoid bone. Characteristically, the tumor can be moved side to side but not up or down, due to its location within the carotid sheath 1.
These tumor may synthesize and secrete catecholamines, although this is less common than with adrenal paragangliomas (pheochromocytomas) 1.
The paraganglioma article includes a general discussion of the pathology of these tumors.
Carotid body tumors are located at the carotid bifurcation with characteristic splaying of the ICA and ECA, described as the lyre sign. In all modalities, the dense vascularity of these tumors is manifested as prominent contrast enhancement.
Contrast-enhanced CT is excellent at depicting these lesions. Typical appearances are:
- soft tissue density on non-contrast CT (similar to muscle)
- bright and rapid (faster than schwannoma) enhancement
- splaying of the ICA and ECA
- iso to hypointense compared to muscle
- salt and pepper appearance when larger, representing a combination of punctate regions of hemorrhage or slow flow (salt) and flow voids (pepper) 3
- intense enhancement following gadolinium
- hyperintense compared to muscle
- salt and pepper appearance also seen on T2
The splaying of the carotid vessels (lyre sign) is again identified with an intense blush in tumor with and 'early vein' seen due to arteriovenous shunting 3.
The ascending pharyngeal artery is the main contributing supply.
Treatment and prognosis
Surgical excision is the treatment of choice. The larger the tumor the higher the risk of operative complications 2. In patients for whom the risk of complications precludes surgery, radiotherapy may be considered 1-2.
Malignant transformation is encountered in 2-36% of cases with metastases most commonly to bone, lung and liver and regional lymph nodes 3.
General imaging differential considerations include:
- 1. Davidovic LB, Djukic VB, Vasic DM et-al. Diagnosis and treatment of carotid body paraganglioma: 21 years of experience at a clinical center of Serbia. World J Surg Oncol. 2005;3 (1): 10. doi:10.1186/1477-7819-3-10 - Free text at pubmed - Pubmed citation
- 2. Bailey BJ, Johnson JT, Newlands SD. Head and neck surgery--otolaryngology. Lippincott Williams & Wilkins. (2006) ISBN:0781755611. Read it at Google Books - Find it at Amazon
- 3. Lee KY, Oh YW, Noh HJ et-al. Extraadrenal paragangliomas of the body: imaging features. AJR Am J Roentgenol. 2006;187 (2): 492-504. doi:10.2214/AJR.05.0370 - Pubmed citation
- 4. Arya S, Rao V, Juvekar S et-al. Carotid body tumors: objective criteria to predict the Shamblin group on MR imaging. AJNR Am J Neuroradiol. 2008;29 (7): 1349-54. doi:10.3174/ajnr.A1092 - Pubmed citation
- 5. Aaron D. Skolnik, Laurie A. Loevner, Deepak M. Sampathu, Jason G. Newman, John Y. Lee, Linda J. Bagley, Kim O. Learned. Cranial Nerve Schwannomas: Diagnostic Imaging Approach. (2016) RadioGraphics. 36 (5): 1463-77. doi:10.1148/rg.2016150199 - Pubmed