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.

Historical Perspective

• Carotid body was first described by Von Haller in 1743.
• The familial form of the carotid body tumor was first described by Chase in 1933.
• Carotid body tumor was first described by Bungeler in 1952.
• The tumor is also called chemodectema, first suggested by Mulligan in 1951.

Classification

• Carotid body tumor is classified into 3 categories:

• Familial carotid body tumor
• Sporadic carotid body tumor
• Hyperplastic carotid body tumor

• Carotid body tumor is sub-classified into 2 categories:

• Single
• Bilateral

• Carotid body tumor may also be classified according to Shamblin surgical classification into 3 subtypes: I, II, and III.

• Class I: localized with minimal vascular attachment
• Class II: partially surrounds carotids.
• Class III: encases carotids.

• The image below demonstrates the distribution of carotid body tumors.

• 

  Distribution of paraganglioma

Pathophysiology

• Carotid body tumor is a neuroendocrine neoplasm originating from carotid body.
  • Carotid body is a component of the autonomic system derived from neural crest cells.
• The overgrowth of chemoreceptor paraganglioma cells in the carotid body leads to the formation of carotid body tumor.
• Carotid body tumors are normally located in the medial aspect adventitia of the carotid bifurcation.
• Carotid body tumor occurs sporadicly in 85% to 90% of the cases.
• The tumor may be bilateral in fewer than 5% of the sporadic cases.
• The tumor may be familial in the rest 10% to 15%.
  • In familial cases, it may be bilateral in 30% to 40% of the cases.
• The genetic mutations associated with the development of carotid body tumor, include:

• MEN 2A
• MEN 2B
• Chromosome 3p25.5

• On gross pathology, characteristic findings of carotid body tumor, include:

• Dusky color
• Highly vascular mass

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.

• 

  Gross pathology of carotid body tumor

• 

  Carotid body tumor higher magnification

• 

  Carotid body tumor lower magnification

Causes

• Common causes of carotid body tumor, include:

• Multiple endocrine neoplasia
• Phakomatoses
• Tuberous sclerosis complex (TS)
• Neurofibromatosis type 1 (NF1)
• Von Hippel-Lindau disease (vHL)
• Carney triad

Differentiating Carotid Body Tumor from Other Diseases

• Carotid body tumor must be differentiated from other diseases that cause rounded neck mass, limited range of head motion, and dyspnea such as:

• Vagal schwannoma
• Vagal neurofibroma
• Lymph node mass
• Glomus vagale tumour
• Carotid bulb ectasia
• Carotid calcification
• Branchial cleft cyst

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.

Risk Factors

• Common risk factors in the development of carotid body tumor, include:

• Genetic mutations in the following genes:

• MEN 2A
• MEN 2B
• Chromosome 3p25.5

Natural History, Complications and Prognosis

• 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.
• Common complications of carotid body tumor, include cranial nerve palsy, stroke, or Horner syndrome.
• Prognosis is generally poor, and the average 5 year survival rate of patients with carotid body tumor is approximately 25-40%.

Diagnosis

Diagnostic Criteria

• The diagnosis of carotid body tumor is made with imaging findings:

• Lyre sign (see Imaging below)
• Early vein due to arteriovenous shunting
• Bright and rapid enhancement
• Family history of the following syndromes (tuberous sclerosis complex, neurofibromatosis type 1, and Von Hippel-Lindau disease)

Symptoms

• Symptoms of carotid body tumor may include the following:

• • Painless mass in the lateral of neck
  • The mass tends to grow slowly
• In case of tumors with greater extension symptoms may include:
  • Horseness due to vagus or laryngeal nerve involvement
  • Involvement of hypoglossal or glossopharyngeal nerves
  • Horner syndrome due to the invasion or compression of the cervical sympathetic chain
  • Syncope due to possible compression of the carotid sinus or internal carotid artery
• Symptoms that may suggest the metastatic activity of the tumor include:
  • Malaise
  • Weight loss
  • Weakness
• Symptoms that may suggest the hormonal activity of the tumor include:
  • Palpitation
  • Tremor
  • Headache due to hypertension

Physical Examination

• Patients with carotid body tumor usually appear pale or diaphoretic.
• Physical examination may be remarkable for:

Palpation

• Palpable, painless, rubbery mass along the anterior border of the sternocleidomastoid muscle.
• The tumor moves freely in the horizontal plane at a greater extent than in the vertical plane (‘Fontaine’s sign’).

Inspection

• Limitation on neck range of motion
• Pharyngeal bulge with the displacement of the tonsil, soft palate, and uvula to the opposite side

Auscultation

• Bruit
• Carotid murmur

Laboratory Findings

• There are no specific laboratory findings associated with carotid body tumor.
• In some cases, genetic testing may be useful for the detection of familial syndromes related with carotid body tumors.

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

• 

  MRA of carotid body tumor

• 

  Carotid body tumor angiography

• 

  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

Treatment

Medical Therapy

• There is no treatment for carotid body tumor; the mainstay of therapy is supportive care.
• Radiotherapy is the treatment of choice for patients without surgery fitness (poor surgical candidates)

Surgery

• Surgery is the mainstay of therapy for carotid body tumor.
• Transcervical surgery approach in conjunction with embolisation are the most common approaches to the treatment of carotid body tumor.
• Stage III Shamblin carotid body tumors (greater than 5 cm) are eligible for surgery only.
• The most common surgical complications of carotid body tumors is injury of the superior laryngeal nerve.

Prevention

• There are no primary preventive measures available for carotid body tumor.