A Vascular Malformation in the Carotid Sheath at the Carotid Bifurcation Mimicking Carotid Body Tumor

Introduction

The carotid sheath includes clinically important and vital anatomical neurogenic, vascular, and lymphatic structures that allow for a great variety of lesions. Masses within this space include paragangliomas, neuromas/neurofibromas, lipomas, vascular anomalies, and pathology involving the deep cervical chain lymph nodes. Among them, vascular anomalies may escape diagnosis, due to their infrequent localization in the carotid sheath. ¹

We present a 60-year-old woman with a vascular malformation arising within the carotid sheath at the right carotid bifurcation. The unique nature of this case is the mass’ unusual presentation that mimics carotid body tumor. This report was deemed exempt from review by our institutional review board and the patient consented to publication of this case report.

Case Report

A 60-year-old woman presented with a 6-month history of a painful mass in the right side of the neck. The patient denied any dysphagia and dysphonia associated with the mass or previous trauma to the neck. A firm 3-cm mass was palpable deep to the right sternocleidomastoid muscle. It was tender, nonpulsatile, and without detectable bruits. It was mobile in the lateral plane, but its mobility is limited in the cephalocaudal direction. No lymphadenopathy was palpated. All laboratory values showed no abnormalities.

Neck sonography showed a solid, well-defined mass with mixed echogenicity and no blood flow signal, measuring 34 mm × 22 mm × 18 mm. It is centered at the carotid bifurcation and causes splaying of the right internal and external carotid arteries (Figure 1A). Contrast-enhanced computed tomography (CT) revealed a 3.6 cm × 2.3 cm × 1.9 cm solid, ovoidal mass centered at the carotid bifurcation that causes splaying of the right internal and external carotid arteries (Figure 1B). Magnetic resonance imaging (MRI) showed a well-defined soft tissue mass that demonstrated isointensity on the T1 weighted and hyperintensity on the T2-weighted MRI (Figure 1C).

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Figure 1.

A, Sonography showed a solid, well-defined mass with mixed echogenicity and no blood flow signal at the right carotid artery bifurcation. B, Contrast-enhanced CT revealed a solid, ovoidal mass centered at the carotid bifurcation that causes splaying of the right internal and external carotid arteries. C, Magnetic resonance imaging showed a well-defined soft tissue mass that demonstrated isointensity on the T1 weighted and hyperintensity on the T2 weighted. CT indicates computed tomography.

Because of the lack of a pathological diagnosis, and the symptom of pain, she was offered surgical excision of the mass. The patient also favored excision and gave informed consent. An encapsulated mass situated between the internal and external carotid arteries at the level of the carotid bifurcation, underneath the hypoglossal nerve, was discovered within the carotid sheath (Figure 2A). The mass was intimately adherent to the bifurcation. The jugular vein, the carotid artery, and the hypoglossal nerve were carefully mobilized away from the mass. The vagus nerve was anatomically unrelated to the mass and was preserved. Two small feeding vessels from external carotid artery were ligated without arterial clamping and the lesion was completely removed. A large number of blood sinuses were found upon incision of the mass (Figure 2B). Histological analysis (hematoxylin-eosin stain ×40) revealed a vascular malformation with thin-walled blood vessels, lined by endothelial cells and separated by fibrous tissue (Figure 3).

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Figure 2.

A, Intraoperative photograph demonstrating dissection of the mass from within the carotid sheath. B, Macroscopic section of the mass revealing a large number of blood sinuses.

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Figure 3.

Histological analysis (hematoxylin–eosin stain ×40) revealing a vascular malformation with thin-walled blood vessels, lined by endothelial cells and separated by fibrous tissue.

Postoperative course was uneventful and the patient was discharged the third postoperative day with instructions for regular follow-up. She was in good clinical condition without signs of relapse of the mass at 6-month follow-up.

Discussion

The carotid sheath contains the carotid artery, the internal jugular vein, the vagus, and the deep cervical lymph node chain. Vascular anomalies found in the carotid sheath are rarely reported and may be easily misdiagnosed as arterial aneurysms, neurogenic tumors, paragangliomas, or lymphatic masses. ^{1 -3} The International Society for the Study of Vascular Anomalies (ISSVA) classified vascular anomalies in vascular tumors and vascular malformations based on clinical and histologic characteristics. ⁴ They can be distinguished by their pathophysiology and morphology. The predominant representatives of vascular tumors, characterized by excessive angiogenesis, based on endothelial cell proliferation, are congenital and infantile hemangiomas. ⁵ Vascular malformations are characterized by defective vessel maturation with a varying degree of mesenchymal tissue proliferation, including dermal, subcutaneous, fatty, and bone tissue. ⁶ These lesions predominately occur within the head and neck. ^7,8 In this case, the mass situated at the right carotid bifurcation splaying the internal and external carotid arteries and was misdiagnosed as carotid body tumor at the beginning. However, it was heterogenous without blood flow signal on sonography, and isointense on the T1 weighted and hyperintense on the T2-weighted MRI, which suggests it was a slow-flow venous malformation. It was obvious that only surgical excision and histologic examination could reveal the true nature of the mass. The excision of these lesions is usually a challenge as venous malformations are rarely well-defined lesions and intraoperative bleeding can make identification and preservation of important structures difficult. ⁹ However, in this case, the mass was well defined, which makes the excision justified.

Neck masses should be investigated carefully with sonography, CT, and MRI to avoid misdiagnosis, as described in this case. The ISSVA classification is an example of well-studied system that allows for appropriate treatment in patients with such lesions.

Conclusion

Vascular malformation is a rare but existing possibility of pathology in the carotid sheath, which can be effectively removed by meticulous surgery.