• carotid body tumor (glomus tumor) is a rare tumor, but it represents the most common extra-adrenal paraganglioma
    • more common in females, typically diagnosed in the 4-5th decade of life
    • most cases are sporadic; 10% are hereditary
      • familial tumors present earlier (typically in the 4th decade) and are more often multicentric
      • there is an association with multiple endocrine neoplasias ( MEN IIa and MEN IIb), tuberous sclerosis complex (TS), neurofibromatosis type 1 (NF1), von Hippel-Lindau disease (vHL)
    • bilateral in approx. 10% of cases
    • histologically similar tumors can also arise from the jugular bulb, sympathetic vagal ganglia of the neck (glomus vagale tumor  Glomus vagale tumor on MRA ), Jacobsen’s tympanic plexus of the middle ear, retroperitoneal sympathetic and visceral parasympathetic ganglia, spinal paragangliomas are rare and occur intradurally extramedullary, usually in the region of the filum terminale/cauda equina, or less frequently extradurally
  • hypervascularization is an essential feature of glomus tumors
  • because of the absence of neuroendocrine secretion, they are classified as chemodectomas (chemoreceptor tumors)
    • in sporadic cases, catecholamine secretion and associated hypertensive symptoms may be present
  • most head and neck paragangliomas are benign, locally invasive
    • approximately 2–13% of paragangliomas demonstrate malignancy
    • malignancy is defined by metastasis, as there are no histopathologic diagnostic criteria that can accurately differentiate between malignant and benign paragangliomas
    • metastases are usually regional (in the neck); distant metastases are rare  (Boedeker, 2007)

Classification

To assess the extent and operability of tumors and to predict postoperative morbidity, the Shamblin Classification is used:

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Clinical presentation

  • most often painless, elastic, pulsating, slowly growing rounded mass in the neck, located anterior to the sternocleidomastoid muscle, near the mandibular angle
  • larger tumors cause head/neck pain, dysphonia, and other symptoms resulting from lesions of multiple cranial nerves (n.IX, X, XI, and XII)
  • on palpation, the mass moves horizontally but not vertically because of fixation at CCA bifurcation (Fontaine’s sign)
  • endocrine activity is less common than in adrenal paragangliomas (pheochromocytomas)
Carotid body tumor (Poprachová, 2012)

Diagnostic evaluation

CT/MRI

CT / CTA

  • the tumor has soft tissue density with rapid enhancement
  • as it grows, a splaying of the origin of ICA and ECA  is visible (“lyra” sign) Carotid body tumor on CT with post-contrast enhancement

    • tumors of glomus vagale or jugulare are located distally   Glomus vagale tumor on CTA
  • CTA shows a hyper-vascularized mass in the carotid bifurcation area with an early vein filling due to arteriovenous shunting   Carotid body tumor on CTA
  • the maximum circumferential contact of the tumor with the ICA on axial images can predict the Shamblin group  (Arya, 2008)

    • group I: <180 degrees of encasement
    • group II: 180-270 degrees of encasement
    • group III: >270 degrees of encasement (probable adventitial involvement with the need for ICA resection
  • T1
    • iso- to hypointense lesion with intense gadolinium enhancement  Carotid body tumor on MRI with post-contrast enhancement
    • the maximum circumferential contact of the tumor with the ICA on axial images can predict the Shamblin group
  • T2
    • salt and pepper appearance  Carotid body tumor on T2
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Neurosonology

  • hypervascularized mass in the carotid bifurcation area   Carotid body tumor on ultrasound
Carotid body tumor on CTA and ultrasound (color flow mode)

DSA

  • the splaying of the carotid vessels (lyra sign)
  • early veins filling due to arteriovenous shunting    Carotid body tumor on DSA with early vein filling

Functional imaging

  • a major advantage of functional (metabolic) imaging is the ability to examine the entire body – useful for detecting multifocal or metastatic disease
  • 123I-metaiodobenzylguanidine (123I-MIBG) scintigraphy
    • suitable for the detection of multiple lesions
    • can only be used in patients with hormonally active tumors
  • 111In-pentetreotide (148 MBq) scintigraphy –  it uses a radiolabeled somatostatin analog that preferentially binds to somatostatin receptor type 2 (SST2), which is most intensely expressed by paragangliomas

    • 111In-pentetreotide scintigraphy is superior to 123I-MIBG scintigraphy in the diagnosis and location of chemodectomas (Muros, 1998)
    • can be used in hormonally inactive tumors
  • 18F-FDG PET – sensitive, but not specific for CBT
    • sensitive for the detection of metastatic disease

Laboratory studies

  • monitoring of plasma levels of catecholamines and their degradation products in urine
    • because of the absence of endocrine secretion in the vast majority of carotid glomus tumors, it is important in the differential diagnosis

If a glomus tumor is suspected, do not perform the biopsy !! (strong vascularization ⇒ high risk of bleeding)

Differential diagnosis

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Management

Surgery

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Radiosurgery

  • carotid body tumors are generally considered radioresistant + tumors treated primarily with radiation are difficult to resect afterward (due to radiation-induced fibrosis) ⇒ surgery is the treatment modality of choice
  • the primary goal of radiotherapy is to slow disease progression
    • radiotherapy is reserved for large or multicentric tumors in patients with contraindications to surgery or unfavorable findings on balloon test occlusion (BTO)
    • radiotherapy may also be used adjuvantly after incomplete extirpation

Prognosis

  • in most cases, a complete cure can be achieved with surgery
  • risk of recurrence ~ 10%
  • tumor growth is slow; therefore, long-term survival is possible even with advanced tumors – an annual mortality rate of <8% has been reported in untreated patients
  • cranial nerve damage caused by tumor compression is usually irreversible
  • follow-up MRI is recommended due to the risk of recurrence or late metastases
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Carotid Body Tumor
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