thyroglossal duct cyst
TRANSCRIPT
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Thyroglossal Duct Cyst
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History• AS, 17, M• CC: anterior neck mass• HPI: 1 year PTC – lump at
right mandible 2 x 2 cms
consulted a PP and advised for UTZ
(+) dysphagia, (+) odynophagia, (+) hoarseness
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History
PMH: unremarkableFMH: unremarkablePSH: 5th of 7 siblings
3rd year high school student frequently absent from school
because of fever NAD, NS
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Physical Examination• Gen survey: conscious,
coherent,
ambulatory, not in CPD
• HEENT: 2 x 2 cm mass at Rt anterior neck
firm, immovable(-) tenderness,(-) swelling(-) CLAD, (-) NVE
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Laboratory Results
• UTZ: ovoid cystic lesions at the front of the neck in the submandibular area near the midline; consider thyroglossal duct cyst; R/O branchial cleft cyst
• Cytopathology: cell findings consistent with chronic lymphadenitis
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Differential Diagnosis
• Thyroglossal Duct Cyst• Branchial Cleft Cyst• Metastatic squamous cell carcinoma• Lymphangioma of neck
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Thyroglossal Duct Cyst
• benign cystic mass • cystic dilations of epithelial remnants of the
thyroglossal duct tract • midline neck masses at the level of the
thyrohyoid membrane and are closely associated with the hyoid bone
• most common congenital cysts of the neck
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• TDC is an embryologic anomaly arising from epithelial remnant left after descent of the developing thyroid from the foramen cecum.
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Initial Thyroid Embryology
• The thyroid gland is the first of the body's endocrine glands to develop, on approximately the 24th day of gestation.
– proliferation of endodermal epithelial cells on the median surface of the developing pharyngeal floor.
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• foramen cecum– Site of initial development– Lies between tuberculum impar and copula– Mesoderm from 2nd pharyngeal pouch– its remains may be observed as a small blind pit in
the midline between the anterior two thirds and the posterior third of the tongue.
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• The thyroid initially develops caudal to the tuberculum impar/the median tongue bud.
– Arises from 1st pharyngeal arch
– midline on the floor of the developing pharynx, eventually helping form the tongue as the 2 lateral lingual swellings overgrow it.
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• THYROID PRIMORDIUM– Initial thyroid precursor– starts as a simple midline thickening and develops
to form the thyroid diverticulum. – initially hollow, although it later solidifies and
becomes bilobed. – The 2 lobes are located on either side of the
midline and are connected via an isthmus.
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Descent of the thyroid gland
• The initial descent of the thyroid gland occurs anterior to the pharyngeal gut.
– At this point, the thyroid is still connected to the tongue via the thyroglossal duct.
• 7-10 weeks AOG – tubular duct solidifies and obliterates completely
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• Pyramidal lobe– may be observed in as many as 50% of patients– Persistence of inferior end of the TGD to obliterate
• Further descent of the thyroid gland carries it anterior (or ventral) to the hyoid bone and, subsequently, anterior (or ventral) to the laryngeal cartilages.
• As the thyroid gland descends, it forms its mature shape, with a median isthmus connecting 2 lateral lobes.
• 7th gestational week,– Thyroid completes its decent, coming to rest in its final
location immediately anterior to the trachea.
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EMBRYOLOGY• 4th week- begins as endodermal
thickening in floor of primitive pharynx
• The thickening becomes an outpouching: thyroid diverticulum
• Thyroid descends anterior to hyoid and thyroid cartilage
• Connected to tongue by thyroglossal duct
• Week 7: Thyroid reaches final position
• Thyroglossal duct has degenerated
• Pyramidal lobe: Persistence of distal end of thyroglossal duct
• Present in 50% of people
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What causes a thyroglossal duct cyst?
• when the thyroglossal tract fails to obliterate at week 10, there may be a persistent hollow tube that may allow accumulation of mucoid material and the formation of a cyst at the end.
• most commonly appears before the age of 5 years, however may present at any age.
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Epidemiology• It is the most common congenital neck mass
• It has a 7% population prevalence.
• The vast majority of patients that have these are very young. Almost half of them are less than 10 years old.
• There is an equal gender distribution, and they are usually asymptomatic.
• Majority of them TGDCs occur in close proximity to the hyoid bone. – 60% - lie just inferior to the hyoid bone at about the level of the thyroid
cartilage– 24% - lie just above the hyoid bone.
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Histologically: well-defined cyst with an epithelial lining.
squamous or respiratory epithelium
find islands of thyroid tissue lying in the walls of these cysts
usually be filled mucoid or mucopurulent material, depending on whether or not the cyst has been infected.
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Clinical Manifestations
• Suddenly appearing• Unsightly or inflamed
midline neck mass• Discovered on routine
exams
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• 1 – 4 cm of midline, overlies hyoid bone
• Anywhere along thyroglossal duct
• Smooth, mobile, no connection with overlying skin
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Diagnosis: TGDC
• Hx / PE–Position of mass–Moves with
swallowing or with protrusion of tongue
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Imaging
• Assess nature of lesion• Determine if mass represents functioning
tissues• UTZ and CT
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• UTZ– Gold Standard– Atypical mass/ location– Distinguish b/w cystic &
solid components– Confirm thyroid location
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• CT Scan– Well – circumscribed
cystic lesion with capsular enhancement.
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• Thyroid Scans– To rule out the cyst containing the only
functioning thyroid tissue.
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Treatment
• Surgery• Sistrunk Procedure
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Indications for Surgery• Cosmesis• Recurrent infections• Fistula formation
• Dysphagia• Dyspnea• Pain
• Treat prior infection before surgery.
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Sistrunk Procedure
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Thyroglossal Duct Cyst
• Thin-walled, • Contains translucent fluid
• VS Dermoid Cyst
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Complications• Post op wound hemorrhage with resultant
airway compromise– Careful hemostasis
• Wound infections– Oral antibiotics
• Carcinoma (1-2%)• Thyroid Ectopia
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Recurrence
• 5% of px, within the year– Inflammation of anterior neck associated with
localized swelling or a draining sinus– Distortion of tissues by inflammation or
inadequate resection of hyoid bone/ carotid stalk leading to foramen cecum
– Presence of multiple tracts– Rupture of cyst at time of incision
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Treatment of Recurrence
• Infection– Oral antibiotics
• Reoperation– Excise widely including inflamed tissues,
remaining hyoid bone & midline genohyoid muscles