• carotid body tumor (glomus tumor) is a rare tumor, but it represents the most common extra-adrenal paragangliomas
    • more common in women, typically diagnosed in the 4th-5th decade
    • most cases are sporadic; hereditary forms account for 10% of cases
      • familial tumors occur earlier (typically in the 4th decade) and are more commonly 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 approximately 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
  • an essential feature of glomus tumors is their hypervascularisation
  • 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 uncommon  (Boedeker, 2007)

Classification

The Shamblin classification is used to assess the extent and operability of tumors and to predict postoperative morbidity:

Content available only for logged-in subscribers (registration will be available soon)

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 resistance is mobile horizontally but not vertically because of fixation at the CCA bifurcation (Fontaine’s sign)
  • endocrine activity is less common than with adrenal paragangliomas (pheochromocytomas)
Carotid body tumor (Poprachová, 2012)

Diagnostic evaluation

Neurosonology

  • hypervascularized mass in the carotid bifurcation area   Carotid body tumor on ultrasound

CT/MRI

CT / CTA

  • tumor has soft tissue density with rapid enhancement
  • as it grows, a splaying of the origin of ICA and ECA (“lyra” sign) is visible 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 of 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
Content available only for logged-in subscribers (registration will be available soon)

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 to allow whole body examination –  useful for the detection of multifocal or metastatic forms
  • 123I-metaiodobenzylguanidine (123I-MIBG) scintigraphy
    • suitable for the detection of multiple lesions
    • can only be used in patients with functional tumors (hormonally active)
  • 111In-pentetreotide (148 MBq) scintigraphy –  it uses a radiolabeled somatostatin analog that preferentially binds to somatostatin receptor type 2 (SST2), which are 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 catecholamine plasma levels and their degradation products in urine
    • because of the absence of endocrine secretion in the vast majority of carotid glomus tumors, it is of a differential diagnostic importance

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

Differential diagnosis

Content available only for logged-in subscribers (registration will be available soon)

Management

Surgery

Content available only for logged-in subscribers (registration will be available soon)

Radiosurgery

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

Prognosis

  • a complete cure can be achieved by surgery in most cases
  • risk of recurrence ~ 10%
  • tumor growth is slow; therefore, long-term survival is possible even with advanced tumors – in untreated patients, an annual mortality rate of < 8% has been described
  • cranial nerve damage induced by tumor compression is usually irreversible
  • because of the possibility of recurrence or late metastases, long-term MRI follow-up is advised
icon-angle icon-bars icon-times