Page 93 - Medicine and Surgery

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Chapter 2: Cardiovascular oncology 89

Aetiology Carotid body tumours
The aetiology of atrial myxoma is unknown.
Definition
Tumour arising from chemoreceptors at the bifurcation
Pathophysiology
of the carotid artery.
The tumour is usually located on a pedicle arising from
the atrial septum, and can grow up to about 8 cm
Incidence
across. The pedicle allows the tumour to move within
Rare
the atrium resulting in various symptom complexes. If
the tumour obstructs the mitral valve a picture similar to Aetiology
mitral stenosis will occur. If the tumour passes through More common in people living at high altitude; it is
the mitral valve, mitral regurgitation will occur. Com- thought that long-term hypoxia is a predisposing factor.
plete mitral valve obstruction may cause syncope. The
tumour may also give rise to thrombosis due to altered Pathophysiology
flow patterns and resultant systemic embolisation. Local Carotid body tumours are hormonally inactive chemod-
invasion and distant metastasis do not occur. ectomas arising from the chemoreceptor tissue of the
common carotid artery at the level of the bifurcation
Clinical features of the artery into internal and external carotid body
The clinical picture varies but the diagnosis is suggested (anatomically at the level of the hyoid bone). The tu-
by features of mitral stenosis with variable cardiac mur- mour tends to grow upwards towards the skull base.
murs and a loud first heart sound especially if coupled
toafever. Many patients have a ‘tumour plop’ in early Clinical features
diastole. Thromboembolism may result from the abnor- Patients present with a pulsatile swelling in the upper
mal flow pattern through the atrium. It occurs in 40% neck at the medial border of the sternocleidomastoid
and is a common presenting feature. muscle. Classically on palpation the lump is mobile from
side to side but not up and down, and there may be an
associated overlying carotid bruit. It is important to dis-
Investigations
tinguish the rare carotid body tumour from the more
ESR is usually raised. Echocardiography demonstrates
common metastatic lymph node from a head and neck
the mass lesion within the atrium.
tumour, which may have transmitted pulsation. Metas-
tasis of carotid body tumours is very rare.
Macroscopy
The tumour is usually a polypoid mass on a stalk, its sur- Microscopy
face covered with thrombus. Histologically the tumour The tumour has a rich blood supply. It is composed of
is made up of connective tissue, with a variety of cell chief cells with clear cytoplasm and a round nucleus en-
typessurrounded by extracellular matrix. closed in a fibrous tissue framework.

Investigations
Management Angiography shows a splaying of the carotid bifurcation
The tumour is surgically removed under cardiopul- (lyre sign). CT and MRI imaging demonstrate the tu-
monary bypass. mour.

Management
Prognosis
Surgical excision may be performed especially in young
Five per cent local recurrence within 5 years. Follow-
healthypatients.Inelderlypatientssurgicalremovalmay
up with regular echocardiography is therefore indicated
not be necessary.
even in asymptomatic patients.