Carotid Body Tumour

🫀 Carotid body tumour is a highly vascular paraganglioma arising from paraganglionic chemoreceptor tissue at the carotid bifurcation. Because it lies in the carotid sheath region, the mass is classically mobile side-to-side but not vertically (Fontaine sign). It usually presents as a slow-growing lateral neck mass and is often benign, but local neurovascular involvement can make management complex.

ℹ️ About

• Also called a carotid body paraganglioma.
• Older terms such as chemodectoma and glomus tumour have been used, although paraganglioma is the preferred modern term.
• It arises from the carotid body, a chemoreceptor organ located at the bifurcation of the common carotid artery.
• Most are slow-growing and non-secretory.

🧬 Pathology and anatomy

• Occurs at the carotid bifurcation, typically separating the internal and external carotid arteries.
• This splaying of the bifurcation on imaging is the classic lyre sign.
• It is a highly vascular tumour, which is why biopsy is generally avoided.
• Large tumours may extend superiorly toward the skull base and may involve adjacent cranial nerves or vessels.

🔬 Histology

• Neuroendocrine tumour composed of chief cells arranged in nests (zellballen pattern).
• Chief cells are surrounded by a delicate vascular stroma and supporting sustentacular cells.
• Histology alone does not reliably distinguish benign from malignant disease; malignancy is defined by metastasis.

📈 Risk factors and genetics

• May occur sporadically or as part of a hereditary paraganglioma syndrome.
• Familial cases are important and are commonly linked to SDHx gene mutations (for example SDHD, SDHB, SDHC).
• They are more common in people living at high altitude and in chronic hypoxic states.
• Reported associations include cyanotic congenital heart disease and severe chronic hypoxia.
• Patients with younger age at presentation, bilateral tumours, multifocal disease, or family history should prompt consideration of genetic testing.

⚠️ Functional activity

• Most carotid body tumours are parasympathetic paragangliomas and are non-secretory.
• Catecholamine secretion is rare, but should be considered if there is headache, palpitations, sweating, or labile hypertension.

🩺 Clinical features

• Slow-growing, painless lateral neck swelling, usually at the anterior border of sternocleidomastoid near the angle of the jaw.
• Classically mobile from side to side but not up and down.
• May be pulsatile; a bruit can sometimes be heard.
• Most patients are otherwise asymptomatic.
• Larger tumours may cause cranial nerve symptoms, dysphagia, hoarseness, tongue weakness, or pain from local compression.

🧠 Differentials

• Reactive or malignant cervical lymphadenopathy.
• Vagal paraganglioma.
• Schwannoma of the vagus or sympathetic chain.
• Branchial cyst.
• Other anterior triangle neck masses.
• Carotid artery aneurysm.

🔎 Investigations

• Ultrasound with Doppler may suggest a hypervascular mass at the carotid bifurcation.
• Contrast-enhanced CT or MRI defines the tumour and its relationship to vessels and skull base.
• MRI may show a vascular “salt-and-pepper” appearance in larger lesions.
• CT angiography or angiography may demonstrate splaying of the carotid bifurcation (lyre sign).
• Consider plasma metanephrines or urinary catecholamine testing if there are symptoms suggesting secretion.
• Consider genetic testing in younger patients, bilateral or multifocal disease, or family history.
• Biopsy is usually avoided because of bleeding risk.

📊 Classification

• Shamblin classification is often used surgically:
• Type I – small tumour, minimally attached to vessels.
• Type II – partially surrounding or adherent to vessels.
• Type III – encasing carotid vessels and technically difficult to resect.

💊 Management

• Management should usually be discussed in a specialist head and neck / skull base MDT.
• Surgical excision is often considered in younger, fit patients, especially for growing tumours.
• Pre-operative embolisation may occasionally be used in selected highly vascular tumours.
• Radiotherapy / stereotactic radiosurgery may be considered where surgery is high risk or for residual/recurrent disease.
• Conservative surveillance may be appropriate in older patients, frailer patients, or very slow-growing asymptomatic tumours.
• Risks of intervention include stroke, major bleeding, and cranial nerve injury.

🚩 Important points

• Most carotid body tumours are benign and slow growing.
• They are not usually malignant; metastatic behaviour is uncommon and is the criterion for malignancy.
• Think about hereditary disease in younger patients, bilateral lesions, or multifocal paragangliomas.
• Do not biopsy routinely because the lesion is highly vascular.

📝 Exam pearls

• Lateral neck mass at carotid bifurcation.
• Moves side to side, not vertically.
• Lyre sign on angiographic imaging.
• Highly vascular paraganglioma.
• Catecholamine secretion is rare.

References

• British Skull Base Society clinical consensus document on management of head and neck paragangliomas.
• GeneReviews: Hereditary Paraganglioma-Pheochromocytoma Syndromes.
• Radiopaedia: Carotid body tumour and lyre sign articles.

Revisions

• Updated terminology to favour carotid body paraganglioma.
• Added genetics, secretion, imaging, Shamblin classification, and the important caution that biopsy is usually avoided.
• Removed weaker syndrome associations and replaced them with the more important SDHx-related hereditary paraganglioma syndromes.