Define Carotid Body Tumour. Describe its clinical features and management.

The Concept

A carotid body tumour (chemodectoma, or carotid paraganglioma) is a rare tumour arising from the chemoreceptor cells of the carotid body, which sit at the bifurcation of the common carotid artery and normally sense blood oxygen, carbon dioxide and pH. It is usually benign and very slow-growing, but its intimate relationship with the carotid vessels makes it surgically important and hazardous. It can be sporadic or familial, and is commoner in people living at high altitude (chronic hypoxia stimulates the carotid body).

Clinical Features — the Diagnostic Signs

It presents as a slowly enlarging, painless, pulsatile lump at the angle of the jaw / upper anterior triangle. Two classic signs reflect its origin at the fixed carotid bifurcation: it is mobile from side to side but not up and down (Fontaine's sign), being tethered to the artery; and it may be pulsatile with a bruit. On angiography or CT it characteristically splays the carotid bifurcation, producing the 'lyre sign'.

Management

Diagnosis is made on imaging — duplex ultrasound, CT/MR angiography — which shows the splayed bifurcation. Biopsy is contraindicated because the tumour is highly vascular. Treatment is careful surgical excision by a vascular surgeon (with the potential need for vascular reconstruction), ideally while the tumour is small, as larger tumours encase the vessels and cranial nerves and are far more dangerous to remove.

A Note on Function

Although derived from chemoreceptor tissue, most carotid body tumours are non-functioning (do not secrete catecholamines); the rare secretory paraganglioma can cause phaeochromocytoma-like symptoms, which is worth screening for before surgery in suspicious or familial cases.

Shamblin Classification & Risk

Carotid body tumours are graded by the Shamblin classification according to how much they encase the carotid vessels (I = localised, II = partially surrounding, III = completely encasing), which predicts the difficulty and vascular risk of excision. This is why early excision while the tumour is small is advised, and why surgery is undertaken by a vascular surgeon prepared for arterial repair. Pre-operative embolisation may be used for large, very vascular tumours to reduce bleeding.

Diagnosis & the Danger of Biopsy

The diagnosis is confirmed by imaging that shows the splayed carotid bifurcation and a highly vascular mass (duplex ultrasound, CT or MR angiography), so that needle or open biopsy is avoided — it risks torrential haemorrhage and offers nothing that imaging cannot. Excision is planned according to the Shamblin grade, with vascular control and the readiness to reconstruct the carotid; familial and multiple tumours prompt genetic assessment and screening for a secretory (catecholamine-producing) paraganglioma before surgery.

The Bottom Line

The core of the carotid body tumour is a pulsatile lump that moves side-to-side but not up-down, splays the carotid bifurcation ('lyre sign'), must never be biopsied, and is excised (graded by Shamblin) by a vascular surgeon — with screening for a secretory paraganglioma in familial cases.

Pulsatile mass at the bifurcation with restricted vertical mobility.

• Carotid body tumour (chemodectoma/paraganglioma) = tumour of carotid body chemoreceptors at the carotid bifurcation; usually benign, slow-growing; familial/high-altitude links.
• Painless pulsatile lump at the angle of the jaw; mobile side-to-side but not up-down (Fontaine's sign); bruit.
• Imaging shows splaying of the carotid bifurcation ('lyre sign'); diagnose with duplex/CT-MR angiography.
• Biopsy contraindicated (very vascular); treat by careful surgical excision (vascular surgeon).