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Glomus Tumor (Head and Neck): Imaging
Updated: Jan 29, 2008
Radiography
Findings
Routine plain-film radiography does not have a role in the diagnosis of glomus tumors.
Computed Tomography
Findings
Contrast-enhanced CT demonstrates enhancing soft-tissue masses at characteristic locations key to diagnosis. Nonenhanced CT imaging can demonstrate glomus tumors, but the demonstration of a strongly enhancing mass is typical in the diagnosis of a glomus tumor.13,19
CT demonstrates carotid body tumors at the level of the carotid bifurcation, respectively splaying the internal and external carotid arteries medially and laterally. These tumors can vary in size, but their location within the bifurcation is critical for diagnosis.
Glomus vagale tumors are masses with similarly strong enhancement. These tumors are seen along the course of the jugular vein and internal carotid artery above the level of the carotid bifurcation but below the skull base. These tumors can vary in size, and they can displace adjacent vascular structures.
Glomus jugulare tumors are enhancing soft-tissue masses at the skull base, but skull-base artifact can mask their presence. These tumors are seen within the jugular foramen; the demonstration of bone erosion of the jugular foramen and petrous apex is often a key finding in the diagnosis. Careful review of bone windows is necessary.
Degree of Confidence
The degree of confidence is high. The presence of strongly enhancing neck masses in typical perivascular locations lead to a high degree of confidence regarding diagnosis.
False Positives/Negatives
Hypervascular lymphadenopathy may result in false-positive findings, which can be seen in a variety of disorders such as metastatic papillary carcinoma of the thyroid gland. In these instances, the location is a key finding.
The lack of sufficient contrast enhancement can be troublesome and may result in false-negative findings. In this case, glomus tumors can mimic schwannomas, neurofibromas, or nonenhancing lymphadenopathies. Potentially, small vascular tumors can be missed if they are not easily distinguishable from the adjacent vascular structures.
Magnetic Resonance Imaging
Findings
Similar to CT imaging, contrast-enhanced MRI demonstrates enhancing soft-tissue masses at characteristic locations; these findings are important for diagnosis. Nonenhanced MRI can demonstrate glomus tumors, but the demonstration of a strongly enhancing mass is typical in the diagnosis of a glomus tumor.19,20,21
As with most soft-tissue tumors, glomus tumors are isointense on T1-weighted MRIs and hyperintense on T2-weighted MRIs, relative to skeletal muscle.
Contrast-enhanced imaging can show intense tumor enhancement, which again is a key finding in the diagnosis. In addition, a salt-and-pepper fine vascular pattern can be seen in the tumors; this finding is suggestive of intrinsic tumor neovascularity and is particularly well demonstrated on T2-weighted images.
MRIs can show densely enhancing carotid body tumors at the level of the carotid bifurcation, which respectively splay the internal and external carotid arteries medially and laterally.
Glomus jugulare tumors are particularly well demonstrated by using MRI. Images show that enhancing soft-tissue masses protrude both intracranially and extracranially at the skull base.
Direct coronal imaging can show tumoral relationships to adjacent structures such as the brainstem and skull base, and deep cervical soft-tissue structures are extraordinarily well depicted.
Degree of Confidence
The degree of confidence is high. Tumor allocation and intense tumor enhancement are of paramount importance in diagnosis.
False Positives/Negatives
Hypervascular lymphadenopathy may result in false-positive findings, which can be seen in a variety of disorders such as metastatic papillary carcinoma of the thyroid gland. In particular, MRI findings can be confusing if T2-weighted images show a salt-and-pepper pattern. In such instances, the location is a key finding.
As with CT imaging, the lack of sufficient contrast enhancement can be troublesome and may result in false-negative findings. In this case, glomus tumors can mimic schwannomas, neurofibromas, or nonenhancing lymphadenopathies if an insufficient amount of contrast material is administered. Potentially, small vascular tumors can be missed if they are not clearly distinguishable from the adjacent vascular structures.
Ultrasonography
Findings
Doppler ultrasonography (US) can demonstrate cervical masses when they are imaged below the angle of the mandible, above the sternum, or in a superficial location not hidden by bone. US can demonstrate the extent of the masses and show their locations. In glomus tumors, the diagnosis of carotid body tumors is possible with US cervical imaging, but US does not suitably reveal the location of glomus vagale, jugulare, and tympanicum tumors.
Because of tumor neovascularity, Doppler US sampling of cervical masses, such as carotid body tumors, can be helpful in diagnosis. In addition, if recognized, increased flow velocities in the external carotid artery or in the jugular vein can provide an indirect clue to the diagnosis of a vascular mass that is above the US imaging field.
Degree of Confidence
The degree of confidence is high if these tumors are found by using US.
False Positives/Negatives
Hypervascular lymphadenopathy can mimic a glomus tumor and cause a false-positive result.
Many glomus tumors are seen in the neck above the level of the mandibular angle, rendering the diagnosis impossible by using US alone; a false-negative finding can result.
Angiography
Findings
Glomus tumors of the head and neck are typically highly vascular, as shown on angiograms. This finding differentiates them from other types of neck neoplasia.
Typical carotid body tumors are situated in the carotid bifurcation and derive their arterial supply from regional external carotid branch arteries. These include the ascending pharyngeal and occipital arteries.
Glomus vagale and jugulare tumors are encountered higher in the neck and at the skull base; therefore, these masses concomitantly involve higher external carotid branch vessels; the ascending pharyngeal, tympanic, and occipital arteries dominate the arterial blood supply. The neovascularity may be extremely intense, and arteriovenous fistulae may be present. Rarely, the internal carotid and vertebral arteries may contribute feeders to the neoplasms. Typically, these tumors are evaluated, with attention paid to all potential feeding arteries. Care is taken to evaluate occult contralateral or ipsilateral masses, which can be occasionally overlooked during cross-sectional imaging.
Degree of Confidence
Degree of confidence is high. The hallmark of a glomus tumor is its intrinsic neovascularity.
False Positives/Negatives
At times, lymph node neovascularity can be difficult to differentiate from glomus tumors. In these situations, the location is a key feature.
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Further Reading
Keywords
chemodectoma, nonchromaffin paraganglioma, glomus body tumors, paraganglioma, glomus jugulare tumors, glomus tympanicum tumors, glomus vagale tumors, carotid body glomus tumors, carotid body tumors
