Carotid body tumor

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Sahar Memar Montazerin, M.D.[2] Maria Fernanda Villarreal, M.D. [3]

Synonyms and keywords: Tumor of the carotid body;

Overview

Carotid body tumor (also known as 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 internal carotid artery and external carotid artery. Carotid body tumor is classified into 3 categories: familial carotid body tumor, sporadic carotid body tumor, and hyperplastic carotid body tumor. The pathogenesis of carotid body tumor is characterized by the overgrowth from chemoreceptor paraganglioma cells. The genetic mutations associated with the development of carotid body tumor, include: MEN 2A, MEN 2B, and chromosome 3p25.5. Common causes of carotid body tumor, include: multiple endocrine neoplasia, phakomatoses, tuberous sclerosis complex (TS), neurofibromatosis type 1 (NF1), Von Hippel-Lindau disease (vHL), and the Carney triad. Carotid body tumors can be multicentric (35-50%) or familial (7-10%). In familial forms, carotid body tumors are usually autosomal dominant in inheritance, and associated with genetic syndromes. The estimated prevalence of carotid body tumor is approximately 1-2 cases per 100,000 individuals worldwide. Patients with carotid body tumor may be initially asymptomatic. Early clinical features include painless neck mass, dysphagia, and limited range of motion in the neck. If left untreated, the majority of patients with carotid body tumor may progress to develop neurological complications. Transcervical surgery approach in conjunction with embolisation are the most common approaches to the treatment of carotid body tumor. other names of the tumor:chemodectoma, endothelioma, glomus caroticum, perithelioma, chromaffinoma and nonchromaffin paraganglioma.

Classification

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  Distribution of paraganglioma

Histology

• On microscopic histopathological analysis, carotid body tumor composed of:
  • The chief or paraganglionic cells composing the predominant part of the tumor and contain eosinophilic grannular materials and oval or round nuclei.
  • The supporting or sustentacular cells responsible for the chemoreceptor activity of the carotid body
• The carachteristic finding of this tumor is:

• Chief cells Arranged in distinctive pattern called cell balls (zellballen)
• Separated by fibrovascular stroma and surrounded by sustentacular cells

• The tumor is highly vascular.

• Positive for chromogranin, synaptophysin, neuron-specific enolase, serotonin, neurofilament and neural cell adhesion molecule; they are S-100 protein negative.
• The sustentacular cells are S-100 positive and focally positive for glial fibrillary acidic protein.
• By histochemistry, the paraganglioma cells are argyrophilic, periodic acid Schiff negative, mucicarmine negative, and argentaffin negative.

• The images below demonstrate gross pathology and microscopic histopathological findings of the carotid body tumor.

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  Gross pathology of carotid body tumor

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  Carotid body tumor higher magnification

• 

  Carotid body tumor lower magnification

Epidemiology and Demographics

• The incidence of this tumor is less than 3 in 100,000 individuals.
• The prevalence of carotid body tumor is approximately 65% of head and neck paraganglioma.
• The prevalence of head and neck paraganglioma is 3% of all paraganglioma.
• The estimated prevalence of parasymapathetic paraganglioma is approximately 1-2 cases per 100,000 individuals worldwide.

Age

• Carotid body tumor is more commonly observed in the adults and particularly in their fifth decade of life.
• In familial cases, the mean age of onset is younger, being the second or fourth decade of life.

Gender

There is no gender preference in the incidence of this tumor according to the recent literature.

Race

• There is no racial predilection for carotid body tumor.

Ultrasound

• Two-dimensional ultrasound-imaging, by itself, is not diagnostic, however, it may be helpful in the diagnosis of carotid body tumor.
• A solid, well-defined, hypoechoic lesion on ultrasound imaging.
• This tumor also causes the displacement of the nearby structures
  • The external carotid artery is usually splayed anteriorly
  • The internal carotid artery and internal jugular vein are moved posteriorly
• On color-doppler ultrasound imaging, the tumor appears hypervascular and the direction of blood flow in the tumor is upward at a greater extent.
  • It is of particular note that, although not common, the tumor may not be hypervascular.
• The combination of B mode ultrasound imaging and color-doppler sonography has been observed to be diagnostic for this tumor.

CT scan

• Enhanced CT is the imaging modality of choice for carotid body tumor.
• On CT scan, carotid body tumor is characterized by the following findings:

• Soft tissue density on non-contrast CT (similar to muscle)
• Bright and rapid (faster than schwannoma) enhancement
• Splaying of the internal carotid artery and external carotid artery.

• Radiological signs for carotid body tumor, include:

• Lyre sign : defined as the splaying of the internal and external carotid by a carotid body tumour (visible on CT angiography)

MRI

• On MRI, findings of carotid body tumor, include:

• T1: iso to hypointense compared to muscle
• Salt and pepper appearance when larger, representing a combination of punctate regions of haemorrhage or slow flow (salt) and flow voids (pepper)
• Intense enhancement following gadolinium
• T2: hyper intense compared to muscle
• Salt and pepper appearance also seen on T2

Gallery

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  MRA of carotid body tumor

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  Carotid body tumor angiography

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  CT scan of carotid body tumor.

Other Diagnostic Studies

• Carotid body tumor may also be diagnosed using angiogram.
• Findings on angiogram may include:

• Vascular blush
• Splaying of the carotids