Thyroglossal Duct Cyst

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

History

PMH: unremarkableFMH: unremarkablePSH: 5th of 7 siblings

3rd year high school student frequently absent from school

because of fever NAD, NS

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

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

Differential Diagnosis

• Thyroglossal Duct Cyst• Branchial Cleft Cyst• Metastatic squamous cell carcinoma• Lymphangioma of neck

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

• TDC is an embryologic anomaly arising from epithelial remnant left after descent of the developing thyroid from the foramen cecum.

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.

• 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.

• 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.

• 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.

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

• 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.

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

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.

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.

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.

Clinical Manifestations

• Suddenly appearing• Unsightly or inflamed

midline neck mass• Discovered on routine

exams

• 1 – 4 cm of midline, overlies hyoid bone

• Anywhere along thyroglossal duct

• Smooth, mobile, no connection with overlying skin

Diagnosis: TGDC

• Hx / PE–Position of mass–Moves with

swallowing or with protrusion of tongue

Imaging

• Assess nature of lesion• Determine if mass represents functioning

tissues• UTZ and CT

• UTZ– Gold Standard– Atypical mass/ location– Distinguish b/w cystic &

solid components– Confirm thyroid location

• CT Scan– Well – circumscribed

cystic lesion with capsular enhancement.

• Thyroid Scans– To rule out the cyst containing the only

functioning thyroid tissue.

Treatment

• Surgery• Sistrunk Procedure

Indications for Surgery• Cosmesis• Recurrent infections• Fistula formation

• Dysphagia• Dyspnea• Pain

• Treat prior infection before surgery.

Sistrunk Procedure

Thyroglossal Duct Cyst

• Thin-walled, • Contains translucent fluid

• VS Dermoid Cyst

Complications• Post op wound hemorrhage with resultant

airway compromise– Careful hemostasis

• Wound infections– Oral antibiotics

• Carcinoma (1-2%)• Thyroid Ectopia

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

Treatment of Recurrence

• Infection– Oral antibiotics

• Reoperation– Excise widely including inflamed tissues,

remaining hyoid bone & midline genohyoid muscles