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OJHAS Vol. 10, Issue 1:
(Jan-Mar 2011) |
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Cervical Thymic Cysts Masquerading as Thyroid Cysts |
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Suma MN, Padmini Jeyachandran, Madhusmita Jena, PS Revadi,
Department of Pathology, MVJ Medical College & Research
Hospital, Bangalore, Karnataka, India. |
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Address for Correspondence |
Assistant Professor,
Department of Pathology,
MVJ Medical College
& Research Hospital,
Dandupalya, Kolathur Post,
Hoskote, Bangalore -
562114, India.
E-mail:
sumasheshuvision2000@yahoo.co.in |
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Suma MN, Jeyachandran P, Jena M, Revadi PS. Cervical Thymic Cysts Masquerading as Thyroid Cysts. Online J Health Allied Scs.
2011;10(1):25 |
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Submitted: Mar 13,
2011; Accepted: March 31, 2011; Published:
April 15, 2011 |
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| Abstract: |
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Two interesting
cases of cervical thymic cyst are reported highlighting
the importance of this entity which can be missed preoperatively . Thymic
cysts are of two types-unilocular and multilocular.
They differ in both macroscopic as well as microscopic findings.
Histopathology helps to identify these cysts.
Key Words:
Cervical thymic
cyst; Unilocular; Multilocular
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Cystic swellings in the neck
have varied etiology and can be a diagnostic dilemma. Thymic cysts are
among the rarest cysts found in the neck.1 A spectrum of abnormalities of the thymus is attributed to the embryonic
cervical descent of the thymic primordium. Sequestrated cystic cervical
thymus is found along a normal path of descent, with or without parathyroid
glands.2 Due to the rarity of this cyst a preoperative diagnosis
is seldom achieved. The purpose of this article is to report 2 distinct
types of cervical thymic cyst masquerading as thyroid lesions.
Our first case was a 55 years old
lady presented to the surgical OPD with swelling in left lower neck
for 1and 1/2 months duration. The swelling was insidious in onset, gradually
increasing in size without any obstructive symptoms. There was no history
of change in voice or difficulty in swallowing. On examination a 6X5
cm soft cystic mass with diffuse margins was seen in lower anterior
part of neck. The swelling was noncompressible, not translucent but
moved with deglutition. Lower border was not felt. USG revealed mild
thyromegaly of left lobe with a cyst attached to it. FNAC revealed cyst
macrophages, lymphocytes and few thyroid follicular cells. Pre-operative
diagnosis was MNG with cyst arising from thyroid. Per operatively, a
translucent cyst closely adhered to the left lobe of the thyroid but
well demarcated from the gland was mobilized and removed along with
the left lobe of the thyroid. Left hemithyroidectomy along with cyst
was sent for histopathological examination. Gross examination of the
specimen revealed left lobe of the thyroid with an attached unilocular
cyst with thin translucent wall measuring 5X5 cm (Fig 1). Cyst was filled
with clear fluid. External surface and luminal surface of the cyst wall
was smooth. Histopathology showed flattened epithelial lining with presence
of islands of thymic tissue composed of Hassall's corpuscles and lymphocytes
(Fig 2).
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| Figure
1: Thin walled unilocular cyst with a part of left thyroid lobe |
Figure 2: Cyst wall lined by bland squamoid epithelium with the wall showing hassall’s corpuscles and
lymphocytes (H&E,X400) |
Second case was a 55 years old
male who presented to the surgical OPD with a swelling in the neck for
one month duration. On examination the swelling moved with deglutition.
It was solitary and cystic measuring 2X3 cm over right side of the neck.
The patient was euthyroid and serum calcium levels were 8.9mg/dl. FNAC
revealed cyst macrophages, cholesterol clefts, lymphocytes and occasional
thyroid follicular cells. So a preoperative diagnosis of cystic nodule
of the thyroid was made. Per operatively, both the lobes of thyroid
appeared normal. The nodule was mobilized from the posterior surface
and was excised from the gland. Part of the right lobe was also excised
with the nodule. On gross examination a part of the right hemithyroid
and an attached cyst measuring 3X3cm was identified. Cyst was multiloculated
with intervening septa and was filled with brownish turbid fluid. Attached
part of the thyroid was unremarkable. Histopathology showed multilocular
cyst lined by low cuboidal to squamous epithelium. The lumen contained
pink eosinophilic material, many cyst macrophages and cholesterol crystals.
Intervening septae were of variable thickness and composed of aggregates
of lymphocytic infiltrate beneath the lining epithelium of cyst along
with areas of haemorrhage (Fig 3). Also seen within the septae were cholesterol
granuloma, multinucleated giant cells and aggregates of lymphocytes
(Fig 4).
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Figure 3: Cyst wall shows papillary outpouchings and is lined by flattened to low cuboidal epithelium. Aggregates
of lymphocyte are seen beneath the epithelium (H&E, x100) |
Figure 4: Cholesterol clefts, multinucleated
giant cells and lymphocytes in the cyst wall (H&E, X400) |
Embryologically, the thymus
along with inferior parathyroids develops as paired structures from
the third branchial pouch around the sixth fetal week.3
The inferior parathyroids separate from the thymic tissue and remain
close to lower pole of the thyroid, while the thymus descends into the
mediastinum.4 Thymic cysts are rare and may be found in
the neck or mediastinum. Males are affected more commonly than females.
Thymic cysts manifest themselves
clinically, predominantly between the ages of 20 and 50 yrs and typically
in asymptomatic patients. Two main groups of thymic cysts occur- congenital
unilocular and acquired multilocular thymic cysts.5
Macroscopically, unilocular cyst has a thin wall and multilocular type
of cyst has a thick wall with pericystic fibrous adhesions. Cyst
contents have a variable consistency – unilocular typically contain
only serous fluid, whereas multilocular lesions are filled with turbid,
cheesy or haemorrhagic material.5 Microscopically- in unilocular
thymic cysts, the epithelial surface of the cyst cavity is lined by
bland squamoid cells and the fibrous wall lacks inflammation, haemorrhage
and granulomas. On the other hand , the epithelial component of multilocular
thymic cyst is often simple cuboidal and may show papillary excrescences.
Abundant lymphocytes, granulation tissue, haemorrhage and cholesterol
granulomas are constant constituents in the fibrous walls and cyst cavities
of multilocular thymic cysts.5
Speer6 while considering
cyst formation within thymic tissue postulated many etiologies. These
included embryonal epithelial remnants, degenerating Hassall’s corpuscles,
infectious and inflammatory pathology and neoplastic, hyperplastic and
involutional changes of the epithelial, lymphoid or connective tissue
and vascular elements of the thymus. Two dominant hypotheses have emerged.
One relates the pathogenesis of cystic cervical thymus to acquired progressive
cystic degeneration of unknown etiology in Hassall’s corpuscles and
the epithelial reticulum of the thymus.7 A second body of
opinion favours cystic change in persistent unincorporated remnants
of the thymopharyngeal duct. The latter hypothesis is well accepted
and most consistent with the developmental anatomy of the thymus while
the multiloculated cyst may reflect the first hypothesis, which is progressive
cystic degeneration of the thymus.
Neck masses moving upwards
on deglutition could be thyroid or thyroglossal cyst in origin. It is
difficult to differentiate between thyroid, parathyroid or thymic swellings
clinically.Third pharyngeal pouch cysts may be asymptomatic, minimally
symptomatic or reach a size that causes obstruction to the larynx and
hypopharynx.8 It can be a diagnostic dilemma and frequently
confused with thyroid or parathyroid swellings, as in our case.
In both the cases that we have
studied, close association of the thyroid yielded few follicular cells
in the FNAC and hence the diagnosis of throid cysts was made pre-operatively.
Finding of cholesterol clefts and large number of lymphocytes- one should
keep thymic cyst in mind. However histopathology revealed the morphology
of thymic cyst- unilocular type in the first case and multilocular in
second case. Well defined Hassal’s corpuscles are seen in unilocular
cyst but may or may not be seen in multilocular cyst as in our cases.
The salient differences between unilocular and multilocular cysts are
mentioned in Table 1.
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Table 1: Morphological differences
between Unilocular and multilocular thymic cysts |
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Unilocular |
Multilocular |
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Developmental |
Acquired- Inflammatory/neoplastic |
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More common in neck |
More in mediastinum |
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Cyst is thin walled
and lumen contain clear fluid |
Cyst wall is thickened and contain
turbid, brownish fluid |
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Thymic tissue always
present |
Thymic tissue may or may not be present |
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From remnants of
thymopharyngeal ducts |
Progressive cystic degeneration of
the thymus due to acquired conditions |
The frequent atrophic condition
of the thymic remnants may require sampling from various portions of
specimen before a diagnosis of thymic cyst could be made.9
Clinically, in most cases, cervical thymic lesions present as a unilateral
asymptomatic neck mass. Differential diagnosis includes branchial cyst,
thyroglossal cyst, cystic hygroma, lymphadenopathy, thyroid and parathyroid
gland lesions, lymphoma or other tumours of the area. It is interesting
that the diagnosis of ectopic thymus and thymic cysts have rarely been
made preoperatively.10
- Georgios T, Dionisios L,
Stamatia V, Georgios A, Georgios D, Tsikou-Papafragou A. Ectopic thymic
cyst in neck. J Larygol Otol 2000;114:318-320.
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Zarbo RJ, Areen RG, McClatchey
KD, Baker SB. Thymopharyngeal duct cyst. A form of cervical thymus.
Ann Otol Lryngol 1983;92:284-289.
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Skandalakis JE, Gray SW,
Todd NW. The pharynx and its derivatives. In: Skandalakis JE, Gray SW
, eds Embryology for surgeons. The embryological basis for the treatment
of congenital anamolies 2nd ed. Baltimore: Williams and Wilkins,
1994. pp 17-64
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Nguyen Q, Tar M de, Wells
W, Crockett D, Cervical thymic cyst: case reports and review of literature.
Laryngoscope 1996;106:247-252.
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Suster S, Rosai J. Multilocular
Thymic Cyst: An Acquired Reactive Process: Study of 18 Cases. Am
J Surg Pathol 1991;15:388-3986.
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Speer F. Thymic cysts. Med Coll Flower Hosp Bull 1938;1:142-150.
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Fielding JF, Farmer AW,
Lindsay WK,Conen PE. Cystic degeneration in persistent cervical thymus.
Can J Surg 1963;6:178-185.
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Dehner LP. Congenital
anamolies of the Head and neck. In Head and Neck Surgical Pathology
Williams and Wilkins. 2001. pp. 1-34
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Prasad KK, Gupta RK, Jain
M, Kar DK, Aggrawal G. Cervical thymic cyst : Report of a case and review
of the literature. Indian J Pathol Microbiol 2001;44(4):483-485.
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Spingland N, Bensoussan AL, Blanchard H, Russo P. Aberrant
cervical thymus in children. Three case reports and review of
the literature. J Pediatr Surg 1990;25:1196-1199.
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