Carotid body tumours.
The carotid body was first described in 1743 by Von Haller as ganglion minitum. Mulligan, in 1950, introduced the term "chemodectoma" to describe a notoriously slow growing benign neoplasm arising from the chemoreceptor system whose location results in diagnostic and therapeutic difficulties. The carotid body is the commonest site of chemodectomas.
In 1880, Riegner described the first operative removal of such a lesion. Subadventitial excision was described by Gordon-Taylor,5 in 1940, when he showed a clevage plane between the tumour and the vessel wall. In 1964, Wilson estimated that only 500 cases had been recorded in the literature. Excision with vascular bypass by means of a graft has been described in cases where the tumour cannot be separated from the vessel wall. With advances in vascular surgery and anaesthesia, complications are rare. Complete cure is possible in most cases which are diagnosed and treated early.
A thirty year old woman presented herself with a progressively increasing swelling of one year's duration in the left side of the neck. She had dysphagia and hoarseness of voice for one month.
On examination, there was an oval swelling, 5 x 3 x 2 cm. under the upper third of the left sternomastoid muscle [Fig. 1], more mobile trasversely than vertically. The swelling showed expansile pulsations and became less turgid on compressing the left common carotid artery proximally. Indirectly, laryngoscopy revealed left vocal cord palsy. Systemic examination was normal. BP was 120/ 70 mm of Hg and did not change on massaging the swelling. A left carotid angiogram showed widening of carotid bifurcation by a vascular mass with a faint tumour blush, suggestive of a carotid body tumour. Serum catecholamines were within normal limits. Other routine investigations were normal.
The neck was explored by a transverse incision under general anaesthesia. The tumour was adherent to the common carotid artery bifurcation and internal jugular vein [Fig. 2]. Excision of the tumour with a vascular bypass with a dacron graft was done after crossclamping the carotid artery for a period of 25 minutes. Glucocorticoids and mannitol were given to combat the effects of cerebral hypoxia. The graft was pulsating well on releasing the clamps. The post-operative course was uneventful. There was no neurological deficit. The patient is alive and asymptomatic one year after surgery. A post-operative carotid angiogram showed a blocked graft with no distal outflow. The vertebral system was prominent. Collaterals were seen developing from the opposite side.
A thirty-five year old man came with a left sided lateral cervical swelling of 8 months' duration. There were no pressure symptoms. On examination, there was a swelling 2 x 3 x 2 cm. on the left side of neck, more mobile transversely than vertically. Pulsations were felt on deep palpation and a faint bruit was heard on auscultation. Carotid angiography [Fig. 3] showed a vascular blush at the widened carotid bifurcation, suggesting a carotid body tumour.
The neck was explored by a vertical incision under general anaesthesia. Subadventitial excision of a fairly vascular tumour at the bifurcation was possible. Small arterial branches arising from the bifurcation had to be ligated. No bypass was necessary. The post-operative recovery was uneventful. The patient is alive and asymptomatic 2 years after surgery.
Histopathology was similar in both the cases [Fig. 4]. Nests of fairly uniform epitheloid cells with finely granular pale eosinophilic cytoplasm, with round or occasionally giant nuclei were seen surrounded by vascular stroma. Endocrine pattern of arrangement was seen at places consistent with their function. Mitotic figures were absent and there were a few neural elements.
Cervical chemodectomas are uncommon lesions. They present as asymptomatic, slowly growing, lateral, cervical swellings in the region of the carotid bifurcation. Pressure symptoms may develop with increasing size.
Diagnosis is not always easy. Careful clinical examination usually reveals signs of increased vascularity such as a thrill or a bruit. The condition is mis-diagnosed pre-operatively in about 30% of the cases, Carotid angiography should be done in all suspected cases. It substantiates the diagnosis, indicates the size and vascularity of the tumour, determines bilaterality, distal intracranial outflow and collateral circulation.,  Tissue diagnosis is not necessary and biopsy may be dangerous. Majority of carotid body tumours are benign but may infiltrate locally. About 3% are malignant. The commonest overt malignant manifestation is local recurrence.
Once diagnosed, excision is the treatment of choice. It is advisable to keep facilities of vascular bypass and grafts ready as subadventitial excision may not always be possible. Ligation of carotid artery is no longer done as it causes more harm than leaving the tumour alone. In inoperable cases radiation therapy is recommended.
The mortality in untreated cases is 8% and the recurrence rate is about 12%. We expect both our patients to do well in future.
The authors thank the Dean, Dr. C. K. Deshpande for granting permission to publish this case report. The authors also thank the Department of Radiology for assisting in the investigations.