HK J Paediatr (new series) 2019;24:158-160

Cervical Thymic Cyst: Case Report

L VU KOVI , S RADOVI , N SORAT, A FILIPOVI

Abstract Introduction: Ectopia of thymic tissue in the neck is well known, while the ectopic thymic cysts areextremely rare. Literature enlists frequency of cervical thymic cysts from 0.3% to 1% of all congenitaltumefactions in the neck area. They are usually diagnosed in early childhood. Case report: A nine-year-old girl was hospitalised at Department of Child Surgery, because of the painless cystic tumour at the leftside of the neck. After the performed diagnostic procedures, a surgical exploration was done. The cystictumour was dissected and sent to histopathological verification. During the histological analysis of thecyst wall, in the part that was 6 mm thick, thymic tissue was detected. Conclusion: Cervical thymic cystsmust be considered in the differential diagnosis of cervical cystic formations, especially in child age andpublications of case reports are important in order of caution when cervical cysts are examined.

Key words Cyst; Neck; Thymus

Department of Pathology, Clinical Centre of Montenegro,Faculty of Medicine, University of Montenegro, Podgorica,Montenegro

L VU KOVI MD, Assistant Professor

Institute for Children's Diseases, Clinical Centre ofMontenegro, Podgorica, MontenegroS RADOVI MDN SORAT MD

Department of Endocrine Surgery, Clinical Centre ofMontenegro, Faculty of Medicine, University of Montenegro,Podgorica, MontenegroA FILIPOVI MD, Assistant Professor

Correspondence to: Dr L VU KOVI

Email: ljvuckovic@gmail.com

Received November 28, 2017

Case Report

Introduction

Pharyngeal system anomalies are common congenitaldisorders. Anomalies of the second pharyngeal archrepresent around 95% of all anomalies created due topharyngeal system development disorder.1

Thymus is developed from the third pharyngeal arch andduring the embryonic development thymus descends fromthe neck towards the anterior upper mediastinum. Theembryonic development of the thymus explains thepossibility of thymic tissue residue in the neck, most oftendiagnosed in childhood.2

Ectopia of thymic tissue in the neck is well known, whilethe ectopic thymic cysts in the neck are extremely rare.3

Literature enlists frequency of cervical thymic cysts from0.3% to 1% of all congenital tumefactions in the neck area.They are usually diagnosed in early childhood, morecommonly in boys. Considering the fact that these are rarelesions, the right diagnosis is not often set preoperatively.Surgical excision and histological analysis usually lead todiagnosis.4,5

In the paper we present a case of a nine-year-old girlwith clinical, radiological and pathohistologicalcharacteristics of a cervical thymic cyst.

Case Report

A nine-year-old girl was hospitalised at the Departmentof Child Surgery, due to diagnostics and treatment of

Cervical Thymic Cyst159

painless cystic tumour at the left side of the neck. The cystictumour was noticed by the parents 4 weeks prior addressingto a doctor, and since then they do not cite significant sizechanges. They deny trauma as an etiological factor, loss ofweight and fever. The cystic tumour was clearly visiblewhen the head of the patient was raised. The cystic tumourwas positioned in the middle third of the neck, in front ofanterior edge of the sternocleidomastoid muscle and it waselastic, painless, and mobile, did not fix the skin and thesurrounding neck structures, and measured 5x3 cm.

The blood test results, as well as the biochemicalanalysis, were within the reference values.

Magnetic resonance showed that in the soft tissues onthe left side of the neck, in the level from the third to theseventh cervical vertebral body, there was an oval, septatedinhomogenic cystic tumour, well circumscripted from thesurrounding neck structures, up to 6 cm in diameter, filledwith liquid content, with suppression of the thyroid glandleft lobe to the front and trachea to the right.

Scintigraphy of the thyroid gland was normal.After the performed diagnostic procedures, a surgical

exploration was done under general anesthesia. The patientwas placed into spinal position with head rotated to theright. An incision was made on the skin, along the frontedge of the left sternocleidomastoid muscle. Subcutaneoustissue has been dissected, as well as the platysma andsuperficial fascia of the neck. Medially from the left externaljugular vein, along the front edge of the sternocleidomastoidmuscle, central parts of the neck have been approached. Acystic tumour mass was detected, with the wider poleextending from the middle part of the cricothyroid cartilage.The tumour was dissected, separated from the musculusomohioideus and neck blood vessels (the left internal carotidartery and the left internal jugular vein). With a further tissuepreparation between the esophagus and the trachea, the leftrecurrent laryngeal nerve was identified, which crosses theinferior left thyroid artery on the front and enters the larynxin the area of the cricothyroid cartilage, thereby preservingits integrity. Then the cyst was mobilised from the leftsuperior thyroid artery which crossed its narrow part. Afterthe separation of left superior thyroid artery, the origin ofcystic tumour in the level of the pre-vertebral fascia of thethird cervical vertebra was dissected.

The cystic tumour was sent to histopathologicalverification (Figure 1).

The pos topera t ive recovery passed wi thoutcomplications.

Using a macroscopic examination, a cystic tumour wasmultilocular, measured 6x3.7x1.5 cm, with smooth externalsurface. Septa were widening from 0.2 to 0.6 cm with smoothinner surface, with lumen filled by yellowish liquid content.

During the histological analysis of the cyst wall, in thepart that was 0.6 cm thick, thymic tissue has been detected,the remaining cyst wall as well as septa, were made frommoderately cellular connective tissue, infiltrated withlymphocytes, while the interior surface of all parts wascoated with flattened regular squamous epithelium (Figure2).

After the cervical thymic cyst was diagnosed, thymictissue has not been detected by the magnetic resonance ofthe thorax.

Figure 1 Resection of neck thymic cyst.

Figure 2 Thymic cyst, microscopic slide, haematoxylin eosin,x10.

Vu kovi et al 160

Discussion

Pharyngeal system is created in the fourth week of theintrauterine development.1

Thymus is made from the ventrolateral surface of thethird pharyngeal arch, in the sixth week of the intrauterinedevelopment. The thymus tissue residue, that may createcysts, can be found from the mastoid region to the anteriorupper mediastinum.5

Thymic cysts are rare, especially with cervicallocalisation. They can be congenital and acquired; also theycan be unilocular or multilocular. Unilocular cysts arecongenital, they have a thin wall, with thymus tissue onthe periphery. Multilocular cysts are acquired; their wall ismade from abundant connective tissue and coated withmultilayered squamous epithelium, single-layered cubical,cylindrical or multilayered cylindrical epithelium. Thethymus tissue residue can be found in the cyst wall, hencefacilitate setting the right diagnosis. The congenital are rarerthan the acquired. The surgical excision is preferredtreatment.3,6

There are numerous pathological changes that can beclinically manifested by cervical tumefaction. In paediatricage, congenital anomalies are the most frequent cause. Indifferential diagnosis, cervical bronchogenic cysts,branchial arches residue, lymphatic malformations,thyroglossal ducts, cystic teratoma, cysts of the parathyroidand thyroid gland and the thymus anomalies are considered.7

Clinically, the cysts are commonly asymptomatic, only6-10% patients have symptoms, such as dysphagia,dyspnoea, stridor, pain, vocal paralysis caused bycompression to the recurrent laryngeal nerve andhoarseness. Thymic cysts in the neck most often appear inthe first decade of life, more commonly in boys, in the lefthalf of the neck, placed deeply behind or in front ofsternocleidomastoid muscle.3,8,9

In about half of cases, the cyst is in contact withmediastinal thymus.10

During respiratory infections, they can be enlarged.Computerised tomography and/or magnetic resonance ofthe neck and thorax, can help in setting the cyst diagnosis,its connection with mediastinum, as well as thymus existencein younger patients of paediatric age, to avoidimmunological dysfunction. Surgical excision could bemethod of choice for treatment, and the final diagnosis isset via pathohistological examination.8

It is important to note that surgical treatment of thethymic cyst in the neck, without adequate radiologicalexamination of the region of the neck and chest, in the adult

age will not lead to disorders in the function of the immunesystem, but in childhood it can lead to immunodeficiency.

Surgical excision of the cervical thymic cyst should beperformed with great precaution due to close anatomicalrelationships with neurovascular elements in the neck suchas: the vagus nerve, the internal jugular vein, carotid artery,as well as the phrenic, hypoglossal and recurrent laryngealnerves.2,5,7

In the given case, the thymus cyst in the neck has beendiagnosed in a girl, nine years old, without connection withmediastinum, while in the subsequent examination thymushas not been found in the mediastinum.

Cervical thymic cysts must be considered in thedifferential diagnosis of cervical cystic formations,especially in child age. Publication of the case report isimportant in order of caution when cervical thymic cystsare examined.

Conflict of Interests

The authors declare that there is no conflict of interests.

References

1. Nayan S, MacLean J, Sommer D. Thymic cyst: a fourth branchialcleft anomaly. The Laryngoscope 2010;120:100-2.

2. Kaufman MR, Smith S, Rothschild MA, Som P. Thymopharyngealduct cyst: an unusual variant of cervical thymic anomalies. ArchOtolaryngol Head Neck Surg 2001;127:1357-60.

3. Chaudhari J, Fernandez G, Naik L, Pirosha A. Intrathyroidalmultiloculated proliferating thymic cyst. Endocr Pathol 2015;26:45-7.

4. Betti M, Hoseini NH, Martin A, Buccoliero A, Messineo A,Ghionzoli M. Cervical thymic cyst in childhood: a case report.Fetal Pediatr Pathol 2015;34:65-9.

5. Michalopoulos N, Papavramidis TS, Karayannopoulou G, et al.Cervical thymic cysts in adults. Thyroid 2011;21:987-92.

6. Suster S, Moran CA. Mediastinum. In: Weidner N, Cote RJ, SusterS, Weiss LM, editors. Modern surgical pathology. 2nd ed.Philadelphia: Saunders Elsevier, 2009:454-516.

7. Terzakis G, Louverdis D, Vlachou S, Anastasopoulos G,Dokianakis G, Tsikou-Papafragou A. Ectopic thymic cyst in theneck. J Laryngol Otol 2000;114:318-20.

8. Mahmodlou R, Gheibi S, Nargesi AA, Mahmoodzadeh R, SalabatiM. Symptomatic cervical thymic cyst: a case report and literaturereview. J Compr Ped 2013;4:147-50.

9. Millman B, Pransky S, Castillo J, Zipfel TE, Wood WE. Cervicalthymic anomalies. Int J Pediatr Otorhinolaryngol 1999;47:29-39.

10. Saggese D, Ceroni Compadretti G, Cartaroni C. Cervical ectopicthymus: a case report and review of the literature. Int J PediatrOtorhinolaryngol 2002;66:77-80.