|Year : 2015 | Volume
| Issue : 1 | Page : 98-100
Cystic schwannoma mimicking a second branchial cleft cyst on computed tomography
Madan Mohan Gupta1, Nandini U Bahri2
1 Department of Radiodiagnosis, Shri M.P. Shah Medical College and Guru Govind Singh Government Hospital, Jamnagar, Gujarat, India
2 Department of Imaging, Shri M.P. Shah Medical College and Guru Govind Singh Government Hospital, Jamnagar, Gujarat, India
|Date of Web Publication||8-Jan-2015|
Madan Mohan Gupta
Department of Radiodiagnosis and Imaging, M P Shah Medical College and Guru Govind Singh Government Hospital, Jamnagar, Gujarat
Source of Support: None, Conflict of Interest: None
Schwannoma of the neck is a relatively uncommon tumor. Schwannoma present as insidious, slow-growing, painless masses, characteristics that often lead to an incorrect diagnosis. Cystic schanommas among schanommas are a rare entity. This is a case report of a cystic schwannoma presenting as the cystic lesion in the neck. We report the computed tomography (CT) findings in a 40-year-old female patient presented with a lateral neck mass histologically shown to be a schwannoma, but having certain radiographic features (like tail sign) commonly considered pathognomonic for a type III second branchial cleft cyst (BCC). It is very necessary to differentiate cystic schwannoma from other cystic lesions preoperatively. CT may misguide us for a benign cystic lesion like second BCC. Contrast magnetic resonance imaging and ultrasound findings are very much helpful in differentiation of cystic schwannoma from other cystic lesions of the neck.
Keywords: Cystic schwannoma, tail sign, type III second branchial cleft cyst
|How to cite this article:|
Gupta MM, Bahri NU. Cystic schwannoma mimicking a second branchial cleft cyst on computed tomography. Med J DY Patil Univ 2015;8:98-100
| Introduction|| |
Schwannoma of the neck is relatively uncommon tumor. Benign cystic mimics are generally soft, slow-growing and painless, making clinical distinction difficult. ,,,, Cross-sectional imaging has become the main-stay of diagnosis for these lesions. , We report the computed tomography (CT) findings in a 40-year-old female patient presented with a lateral neck mass histologically shown to be a schwannoma. However, the patient was having certain radiographic features (like tail sign) commonly considered pathognomonic for a type III second branchial cleft cyst (BCC). However, contrast magnetic resonance imaging (MRI) and ultrasound had contributory influence in the diagnosis of cystic schwannoma.
| Case Report|| |
A 40-year-old female patient presented with a painless swelling on the left side of the neck for the last 2 years. Evaluation by an otolaryngologist revealed a smoothly marginated, nontender, palpable, slightly mobile, left upper neck mass. The remainder of the examination was unremarkable.
Ultrasound reports revealed a well-circumscribed hypoechoic soft-tissue lesion with internal vascularity [Figure 1]. Further, the patient was referred for contrast enhanced CT. A well-circumscribed, sharply marginated, nonenhancing low attenuation lesion (10-25 HU) was noted in left carotid space on contrast enhanced CT. The lesion lies antero-medial to left sternocleidomastoid muscle, lateral to carotid vessels and posterior to the left submandibular gland [Figure 2]. The lesion causes displacement of the internal carotic artery antero-medially and internal jugular vein (IJV) antero-laterally. The lesion demonstrates a small tail extending between the internal carotid artery (ICA) and the external carotid artery just above the carotid bifurcation [Figure 3]a. The lesion also splayed the left common carotid artery and IJV [Figure 3]b. Further, contrast MRI was done for better soft-tissue characterization. On noncontrast MRI, the lesion revealed hyperintense signal intensity on T2-W [Figure 4]a, short tau inversion recovery images [Figure 4]b and hypointense signal intensity on T1-W image [Figure 4]c. Homogenous enhancement was noted on post contrast 10 min delayed T1-weighted fat saturated sequence [Figure 5]a. The lesion also demonstrated a small tail extending between the ICA and the external carotid artery similar to CT [Figure 5]b. On ultrasound guided fine needle aspiration cytology, aspirated material showed clusters of spindle cells and verocay bodies and cyst on H and E stain [Figure 6]a. Histopathological examination of resected specimen confirmed the diagnosis of cystic schwannoma of vagus nerve (Antony B type). Microscopically, dense tumor showed spindle cells in palisading pattern with central cystic areas and peripheral stroma showed mucous degeneration [Figure 6]b.
|Figure 1: A 40-year-old female with cystic schwannoma of the vagus nerve, ultrasound image shows well-circumscribed, smooth marginated, heterogenous hypoechoic lesion with internal vascularity on color Doppler (arrow)|
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|Figure 2: Contrast enhanced computed tomography axial image shows a well-circumscribed, sharply marginated, nonenhancing low attenuation lesion in the left carotid space (line arrow). The lesion lies anterior and medial to the left sternocleidomastoid muscle (small arrow), lateral to carotid vessels (curved arrow), just below the left angle of mandible and posterior to the left submandibular gland (large block arrow)|
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|Figure 3: Contrast enhanced computed tomography axial images: (a) Shows a small tail (arrow) extending between the internal carotid artery (ICA) and the external carotid artery just above the carotid bifurcation with displacement of ICA antero-medially and internal jugular vein (IJV) antero-laterally and (b) shows splaying of left common carotid artery (large arrow) and IJV (small arrow)|
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|Figure 4: Noncontrast magnetic resonance imaging: (a) T2-W axial image the lesion shows homogenous hyperintense signal intensity (arrow); (b) short tau inversion recovery coronal image shows hyperintense signal (arrow) and (c) T1-W axial image shows hypointense signal intensity (arrow)|
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|Figure 5: Contrast magnetic resonance imaging: (a) On 10 min delayed scan, the lesion shows homogenous enhancement (arrow) and (b) small part of lesion is extending between the internal carotid artery and the external carotid artery just above the carotid bifurcation suggests small tail (arrow)|
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|Figure 6: Microscopic examination: (a) Fine needle aspiration cytology shows clusters of cells and verocay bodies and cyst on H and E, (×40); (b) histopathological examination of tissue biopsy shows spindle cells in palisading pattern with central cystic areas and peripheral stroma shows mucous degeneration|
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| Discussion|| |
Verocay first reported Schwannoma in 1910. These lesions represent solitary neurogenic tumor arising from the cells forming the neural sheath. Schwannomas in the head and neck region most frequently occur as vestibular schwannoma on the superior aspect of the vestibular nerve, but cystic variants comprise only about 4%. Although schwannoma often presents as a solitary, painless and slow-growing mass of variable size, cystic schwannoma is thought to grow more rapidly than noncystic schwannoma. These cases become a potential diagnostic challenge, as these will have similar presentation as BCCs.
On ultrasound, cystic schwannoma looks like any other cystic lesion but demonstrates wider tissue heterogeneity. Gritzmann et al. reviewed the utility of sonography in evaluating soft-tissue masses of the neck. Their review ended by stating that BCCs have the variable echogenicity, but on color Doppler imaging, no vascularity is noted.  By contrast, schwannomas show internal vascularity on color Doppler imaging that can easily be identified. 
Visualization of the cyst's extension or "tail" between the ICA and external carotid artery is considered pathognomonic for type III BCC. ,, Type III BCCs extend farther medially between the internal carotid artery and external carotid artery at the carotid bifurcation. Visualization of the cyst's extension or "tail" between the internal carotid artery and external carotid artery considered pathognomonic for type III BCCs. 
Most of these tumors are benign, if symptomatic, may require surgical excision to preserve nerve function. , Diagnosis usually requires a combination of radiographic assessment and surgical pathological correlation. Schwannomas have been described as hypo-, iso-, or hyper attenuated with variable texture (heterogeneous or homogeneous) and patchy enhancement on CT. The heterogeneity has been attributed to cystic degeneration, xanthomatous change, or areas of relative hypocellularity adjacent to densely cellular or collagenous regions. The MRI finding of cystic schwanomma shows low-to-intermediate signal intensity on T1-WI, heterogeneous hyperintensity on T2-WI, and intense heterogeneous postgadolinium enhancement. The classical imaging appearance for a schwannoma of the neck is a large, sharply demarcated, fusiform enhancing mass in the region of the jugular foramen or parapharyngeal space. ,
| Conclusion|| |
We conclude that cystic schwanommas are rare differential of cystic masses of neck and one should consider with high level of suspicion whenever there is rapidly growing cystic lesion in neck without pain and showing variable echogenicity on ultrasound along with tail sign on CT with patchy enhancement on contrast enhanced CT. Nevertheless, tissue diagnosis remains the confirmative test.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]