Year : 2000 | Volume
: 10 | Issue : 1 | Page : 39--40
US and CT in carotid body tumor
DS Dhiman, YP Sharma, NK Sarin
Dept of Radiology, I G Medical College, Shimla, Himachal Pradesh, India
D S Dhiman
Dept of Radiology, I G Medical College, Shimla-171 001, Himachal Pradesh
|How to cite this article:|
Dhiman D S, Sharma Y P, Sarin N K. US and CT in carotid body tumor.Indian J Radiol Imaging 2000;10:39-40
|How to cite this URL:|
Dhiman D S, Sharma Y P, Sarin N K. US and CT in carotid body tumor. Indian J Radiol Imaging [serial online] 2000 [cited 2020 May 28 ];10:39-40
Available from: http://www.ijri.org/text.asp?2000/10/1/39/30633
Glomus tumors classified as chemodectomas are rare tumors arising from the chemoreceptor system in the head or neck region. The most common non-adrenal paraganglioma to present as a neck mass at the carotid bifurcation is the carotid body tumor (CBT) primarily located in the adventitial layer of the blood vessels. These arise from the non-chromaffin paraganglion cells, which microscopically appear as small capillaries surrounded by epitheloid (chief) cells and ultrastructurally contain catecholamine-bound neurosecretory granules.
CBTs may show a familial pattern with bilateral involvement or multicentricity. They may be associated with other tumors such as pheochromocytoma or other cervical chemodectomas.
Initially, CBTs appear as slowly growing, asymptomatic palpable masses in the anterior triangle of the neck. Untreated, these tumors tend to surround the external and internal carotid arteries without any significant compression. Continued growth leads to cranial nerve involvement, pharyngeal compression and skull base and intracranial invasion. The sympathetic chain and internal jugular vein may also be involved by larger tumors. In addition to painless masses patients may present with pain, hoarseness, dysphagia, Horner's syndrome, tongue paresis and vertigo . Functional i.e. catecholamine secretory, carotid body paragangliomas are rare and can produce paroxysmal hypertension mimicking a pheochromocytoma .
CBTs occur more frequently in adults averaging 45 to 50 years of age and are uncommon in children. Sporadic forms of CBT are more frequent. Familial forms account for 10% in most series with bilateral tumors seen in 30% of cases. In sporadic cases, a bilateral tumor is detectable in only 5% of patients . While the majority of these tumors are benign, 2-13% pursue a malignant course with metastases to regional lymph nodes, lungs and bones.
Paragangliomas of the neck are uncommon tumors whose proper care requires accurate diagnosis and skilled surgical treatment. The differential diagnosis of an incidentally observed non-tender antero-lateral neck mass includes metastatic lymph nodes, carotid body aneurysm, salivary gland tumor, branchial cleft cyst and thyroid and neurogenic tumors. Although arteriography is considered mandatory and remains the gold standard for diagnosis, noninvasive imaging studies are frequently adequate for workup of suspected CBTs.
On ultrasonography (US), the demonstration of a solid, well-defined, weakly echogenic mass located within the carotid bifurcation safely differentiates and excludes purely cystic masses. High frequency high resolution US depicts accurately the location, shape of the disease process and anatomic relationship of the tumor with the vessels of the neck and demonstrates multiplicity of nodules if any [Figure 1]. Doppler analysis of the mass demonstrates low resistance arterial blood flow within the mass. This helps in differentiating CBTs from other solid non-hypervascular neck masses such as lymph nodes, metastases, salivary gland tumors or cervical cysts. Doppler color flow US may show identification of intra-tumoral blood vessels that may not be visible with US imaging alone . Tumor masses appear hypoechoic and solid, interlaced by many fine vascular channels, splaying the carotid bifurcation.
CT demonstrates a solid mass that shows homogenous enhancement on intravenous contrast administration. The presence of uniform contrast enhancement and large feeding vessels into the tumor is not seen in lymph node masses and schwannomas. The incorporation of large feeding vessels is typical of carotid body paragangliomas whereas schwannomas tend to displace the adjacent vessels. The medical displacement of the internal carotid artery is considered to be specific for tumors of vagal origin whether they are schwannomas or paragangliomas . CT is also useful in evaluating the medial and lateral extent of the tumor, bone involvement and relation to the skull base. The vascular nature of the tumor is well demonstrated on dynamic CT and can be more clearly seen with spiral CT angio [Figure 2],[Figure 3].
Arteriography, the gold standard for diagnosing CBTs, demonstrates a pathognomonic tumor blush as well as the feeding vessels of the tumor; and is an excellent screening tool for concomitant paragangliomas.
On MR, non-contrast T1W images demonstrate a heterogeneous mass with isointense signal intensity at the carotid artery bifurcation with multiple serpentine areas of low signal intensity representing flow voids throughout the mass. On T2W images the tumor shows hyperintense signal intensity. On intravenous gadolinium DTPA contrast administration, the tumor enhances intensely . Neck masses with areas of signal void on MRI such as nodal metastasis from renal cell or thyroid carcinoma do not show displacement of the great vessels of the neck. MR angiography demonstrates splaying of the carotid arteries and may show visualization of feeder vessels to the tumor.
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