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IMAGE CHALLENGE
Year : 2021  |  Volume : 4  |  Issue : 3  |  Page : 547-550

Potato in the parapharyngeal space


Department of Radiodiagnosis, Tata Memorial Hospital, Homi Bhabha National Institute, Mumbai, Maharashtra, India

Date of Submission02-Jul-2021
Date of Decision16-Sep-2021
Date of Acceptance17-Sep-2021
Date of Web Publication08-Oct-2021

Correspondence Address:
Abhishek Mahajan
Department of Radiodiagnosis, Tata Memorial Hospital, Mumbai - 400 012, Maharashtra
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/crst.crst_152_21

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How to cite this article:
Bornak G, Patil V, Mahajan A. Potato in the parapharyngeal space. Cancer Res Stat Treat 2021;4:547-50

How to cite this URL:
Bornak G, Patil V, Mahajan A. Potato in the parapharyngeal space. Cancer Res Stat Treat [serial online] 2021 [cited 2021 Dec 9];4:547-50. Available from: https://www.crstonline.com/text.asp?2021/4/3/547/327761




  Case History Top


A 45-year-old female patient with no comorbidities presented with a right-sided painless neck swelling which had gradually increased in size over the past 4 years. She also complained of difficulty in swallowing for 1 month. On examination, a non-tender, compressible mass was palpated on the right side extending from the tip of the mastoid to the hyoid bone. Pulsations were felt over the mass and a faint bruit was heard on auscultation. The mass was mobile horizontally but fixed vertically. There were few small palpable right level IB and II nodes.

Fine-needle aspiration cytology was done from the right level IB node and was suggestive of reactive lymphadenitis. Magnetic resonance imaging (MRI) was done for further evaluation [Figure 1] which revealed a T1 hypointense, T2 intermediate, intensely enhancing mass with multiple flow voids epicentered at the right common carotid artery bifurcation with associated splaying of the right external carotid artery (ECA) and internal carotid artery (ICA). The mass showed restricted diffusion with intense enhancement and early washout on dynamic contrast-enhanced MRI (DCE-MRI) suggestive of Type 3 curve. Magnetic resonance angiogram (MRA) was performed which demonstrated the classical “Lyre sign” (due to the splaying of the ECA and ICA) and multiple tiny feeder vessels [Figure 2].
Figure 1: (a-d) Axial T1, T2 weighted and diffusion-weighted magnetic resonance imaging at the level of carotid bifurcation and coronal STIR sequence demonstrates a well-defined, lobulated T1 hypointense, T2 intermediate signal intensity mass at the right common carotid artery bifurcation with complete encasement of the external carotid artery and internal carotid artery (Shamblin III). Multiple flow voids are seen within the mass (block arrows), suggestive of a highly vascular nature. There is associated splaying of the right external carotid artery and internal carotid artery. Note the normal alignment of the external carotid artery and internal carotid artery on the left (curved arrow). (e) Sagittal T2-weighted magnetic resonance imaging shows splaying of the right external carotid artery and internal carotid artery. This is characteristic of carotid paraganglioma as opposed to vagal paraganglioma which displaces the external carotid artery and internal carotid artery together. (f) The mass shows intense, homogeneous post-contrast enhancement. (i-iv) Diagrammatic representation of Shamblin classification which is based on the maximum degree of circumferential contact of the tumor with the internal carotid artery. In this particular case, Shamblin IIIa was assigned

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Figure 2: (a-d) Dynamic contrast-enhanced magnetic resonance imaging shows intense homogeneous post-contrast enhancement with rapid washout (Type 3 curve). (e) Magnetic resonance angiogram demonstrates the classic “Lyre Sign” which is due to the splaying of the internal carotid artery and external carotid artery by the tumor. Also, note multiple tiny feeders (block arrow) around the bifurcation

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What is the diagnosis, and what should be done next? Once you have finalized your answer, turn to the next page to read on.

Differential diagnosis and further management

The differential diagnoses that were considered were carotid body tumor, schwannoma, and vagal paraganglioma. Vagal paragangliomas displace the carotids anteriorly rather than splaying them. Schwannomas are rarely pulsatile in nature and may be hypovascular or moderately vascular, as opposed to this case where the mass showed intense vascularity. Doppler study revealed a large hypoechoic mass extending from the tip of the mastoid to the hyoid bone with low resistance flow patterns which is typical for a paraganglioma. The diagnosis of a carotid body tumor was further supported by the pathognomonic “Lyre sign,” intensely vascular mass and Type 3 curve on DCE-MRI. Hence in the given clinical setting and after reviewing the radiological features, a diagnosis of carotid body tumor was made. In view of its solitary nature and the absence of distance metastases, the patient was advised surgery with placement of an ICA graft. The patient is scheduled for surgery and has been asked to undergo the pre-anesthesia workup.


  Discussion Top


Paragangliomas arise from the paraganglion cells which form the basis of the extra-adrenal neuroendocrine system. They are very typical in location and arise in the carotid space, jugular foramen, middle ear, and along the course of the vagus nerve. About 40% of the paragangliomas are familial; these tend to occur early (30–35 years) and are often multicentric.[1] Hereditary paragangliomas are associated with multiple endocrine neoplasia 2B and Von-Hippel–Lindau syndromes. Some form a part of the familial paraganglioma–pheochromocytoma syndrome which is associated with mutations in one of the three subunits of succinyl dehydrogenase (SDH) genes. SDH-B, SDH-C, and SDH-D germline mutation testing can be used for the diagnosis of these variants. A female preponderance is seen with a female-to-male ratio of 1.9:1. All paragangliomas consist of two types of cells; nests of chief cells (Type I) (also known as zellballen) and they are surrounded by a single layer of sustentacular cells (Type II). Paragangliomas are rarely malignant (<10% of cases are malignant); nodal metastasis is the only reliable marker of malignancy as there are no histopathological criteria for differentiating between benign and malignant tumors.[1],[2]

Carotid body tumors, also known as chemodectomas, arise from the chemoreceptors which are present at the carotid bifurcation. These are slow-growing, painless masses which are mobile laterally but fixed vertically (Fontaine's sign). As these tumors enlarge in size, they may lead to dysphagia, hoarseness of voice, Horner's syndrome, and drooping of the shoulder. There is a slightly increased incidence of carotid paragangliomas in patients residing at high altitudes and in the setting of chronic obstructive pulmonary disease.[1]

On ultrasonography, paraganglioma is seen as a well-defined, hypoechoic mass at the carotid bifurcation with significant vascularity on color Doppler. Waveform analysis shows internal arterial flow of the lesion which demonstrates low resistance characteristics.[2]

MRI findings include a T1 hypointense and T2 isointense to hyperintense mass with internal flow voids. Large masses (typically >1 cm) show areas of hemorrhage intermixed with internal flow voids giving it the characteristic “salt and pepper” appearance. Paragangliomas show significantly low apparent diffusion coefficient values. DCE-MRI reveals early peak and washout (Type 3 curve); this can be attributed to the malignant arteriovenous anastomoses and hyperpermeability of the newly formed capillaries within the tumor. Both these features are atypical for benign tumors. Computed tomography scan is the modality of choice for assessing osseous involvement.[2]

Surgery, radiotherapy, and stereotactic radiosurgery are used for the management of carotid paragangliomas. Tumors are divided into three groups based on the Shamblin classification [Figure 1] which is a predictor of vascular morbidity based on the maximum degree of circumferential contact of the tumor with the ICA. MRI can accurately predict and improve the operative outcome. However, there are certain loopholes in the Shamblin classification. The classification does not take into account the size of the tumor and cannot predict the infiltration into the carotid wall. Considering this, modification of the Shamblin classification was proposed which takes into account both the horizontal encasement of the carotid arteries and the vertical extension of the tumor. The proposed classification divides the tumors into Types I-V; the superior margin of the tumor in Type I lying entirely below the angle of mandible; lying between mandibular angle and the mastoid tip in Type II–IV with no encasement, partial and complete encasement of the ICA and ECA, respectively; and Type V includes the tumors in which the superior margin lies entirely above the mastoid tip.[1],[3],[4]

Pre-operative embolization can be performed for large and highly vascular tumors. This typically includes embolization of the ascending pharyngeal branch of the ECA which leads to an almost 75% reduction in the vascular supply and is done 1–2 days before the surgery. The balloon occlusion test is done on the ICA on the affected side and the patient is assessed for neurologic changes. The patient's blood pressure is lowered to simulate mild hypotension. If the patient does not experience any symptoms, then it is assumed that the patient will tolerate ICA ligation without reconstruction. Radiotherapy is useful in cases of large unresectable tumors and multicentric disease.[3],[4],[5]

Paragangliomas being neuroendocrine tumors express somatostatin receptors enabling imaging with Ga-68 DOTA-coupled peptides. These are particularly useful in multicentric disease caused by a germline mutation ( SDH-B mutation). However, Ga-68 DOTATATE demonstrates superior tumor-to-background contrast with identification of a greater number of metastases as compared to fluorodeoxyglucose. Many patients with paragangliomas demonstrate elevated serum catecholamine levels which lead to activation of brown fat throughout the body. DOTATATE is also superior in this regard as it differentiates the lesions from brown fat uptake which is otherwise not possible on positron-emission tomography scan. DOTATATE can also be used for response assessment and for follow-up assessment in patients undergoing treatment.[6]

Differential diagnoses of carotid paragangliomas

Carotid body tumors should be distinguished from other masses in the neck originating from the carotid space [Table 1][1],[2],[7],[8]
Table 1: The three most common differentials to be considered in the diagnosis of carotid body tumors

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  1. Schwannoma: Schwannoma in the carotid space can involve the IX, X, and XII cranial nerves, and the sympathetic chain. MRA can be used to differentiate between a schwannoma and carotid body tumor
  2. Vagal paraganglioma: Vagal paragangliomas account for <5% of the head-and-neck paragangliomas. They have similar imaging characteristics to carotid body tumors. Vagal paragangliomas displace the carotid vessels anteriorly in contrast to carotid body tumors which cause splaying of the carotid vessels
  3. Carotid artery aneurysm/pseudoaneurysm: MRA will reveal a change in the caliber of the artery in case of an aneurysm. On Doppler, the swirling of blood in the aneurysmal sac can create the “yin-yang” sign. Differentiation between a pseudoaneurysm and carotid body tumor is simple, as a pseudoaneurysm contains blood
  4. Very rarely, a lateral ectopic thyroid can also present in this location and can be confused for carotid body tumor.



  Conclusion Top


Carotid body tumors are rare, slow-growing masses which arise from the chemoreceptors at the carotid bifurcation. MRI can be used for accurately diagnosing and predicting the operative outcome. Surgery is the mainstay of treatment for these masses and the Shamblin classification which is based on the degree of circumferential contact of the mass with the ICA is used to predict the operative outcome. Gallium DOTATATE study is useful in multicentric disease and for response assessment and follow-up in patients undergoing chemoradiation.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given her consent for her images and other clinical information to be reported in the journal. The patient understands that her name and initials will not be published and due efforts will be made to conceal her identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Thelen J, Bhatt AA. Multimodality imaging of paragangliomas of the head and neck. Insights Imaging 2019;10:1-9.  Back to cited text no. 1
    
2.
Yuan Y, Shi H, Tao X. Head and neck paragangliomas: Diffusion weighted and dynamic contrast enhanced magnetic resonance imaging characteristics. BMC Med Imaging 2016;16:1-6.  Back to cited text no. 2
    
3.
Arya S, Rao V, Juvekar S, Dcruz AK. Carotid body tumors: Objective criteria to predict the Shamblin group on MR imaging. AJNR Am J Neuroradiol 2008;29:1349-54.  Back to cited text no. 3
    
4.
Gu G, Wu X, Ji L, Liu Z, Li F, Liu B, et al. Proposed modification to the Shamblin's classification of carotid body tumors: A single-center retrospective experience of 116 tumors. Eur J Surg Oncol 2021;47:1953-60.  Back to cited text no. 4
    
5.
Wreesmann VB, Nixon IJ. A novel classification of carotid body tumors. Eur J Surg Oncol 2021;47:1813-5.  Back to cited text no. 5
    
6.
Chang CA, Pattison DA, Tothill RW, Kong G, Akhurst TJ, Hicks RJ, et al. (68) Ga-DOTATATE and (18) F-FDG PET/CT in paraganglioma and pheochromocytoma: Utility, patterns and heterogeneity. Cancer Imaging 2016;16:1-2.  Back to cited text no. 6
    
7.
Hoang VT, Trinh CT, Lai TA, Doan DT, Tran TT. Carotid body tumor: A case report and literature review. J Radiol Case Rep 2019;13:19-30.  Back to cited text no. 7
    
8.
Mohammad A, Iqbal MA, Wadhwania A. Schwannomas of the head and neck region: A report of two cases with a narrative review of the literature. Cancer Res Stat Treat 2020;3:517-25.  Back to cited text no. 8
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    Figures

  [Figure 1], [Figure 2]
 
 
    Tables

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