Congenital Neck Masses

Congenital neck masses are developmental anomalies presenting as a palpable or visible neck mass in infants, children, or sometimes young adults. They arise from incomplete regression or obliteration of specific embryological structures during fetal development.

The main entities are:

• Thyroglossal duct cyst: the commonest, arising from remnants of the thyroglossal duct along the path of thyroid descent from the tongue base to its normal cervical position.
• Branchial cleft anomalies: from incomplete obliteration of the embryological branchial apparatus. Second branchial cleft anomalies are the commonest subtype.
• Less commonly, dermoid cyst and vascular or lymphatic malformations.

Accurate classification by anatomical location and characteristic clinical features is essential, because management, and specifically surgical technique, differs for each entity.

Classification and embryology

• Thyroglossal duct cyst arises from incomplete obliteration of the thyroglossal duct, the tract along which the thyroid migrates from its origin at the tongue base (foramen caecum) to its final position in the anterior neck.
• The cysts are characteristically midline, most commonly at or just below the level of the hyoid bone. They move upward with tongue protrusion or swallowing because of the direct embryological connection to the tongue base via the thyroglossal tract. This is an important distinguishing feature.
• Branchial cleft anomalies arise from incomplete obliteration of the branchial (pharyngeal) apparatus. Second branchial cleft anomalies, the commonest subtype, characteristically present as a mass or sinus tract along the anterior border of the sternocleidomastoid muscle, reflecting the embryological path of this remnant.
• Dermoid cysts arise from entrapped ectodermal tissue along embryological lines of fusion. They present as a midline neck mass that, unlike thyroglossal duct cyst, does not move with tongue protrusion, as there is no connection to the thyroglossal tract.
• Ectopic thyroid tissue is an important consideration in any midline neck mass. In some individuals with a thyroglossal duct cyst, or ectopic thyroid along the thyroglossal tract, this tissue is the only functioning thyroid tissue.
• Inadvertent surgical removal without recognising this risks leaving the patient permanently hypothyroid. This is a critical diagnostic consideration.

• Thyroglossal duct cyst presents as a smooth, mobile, midline neck mass, most commonly at or near the level of the hyoid bone. It moves upward on tongue protrusion or swallowing because of its direct embryological connection to the tongue base.
• The mass sometimes becomes apparent or noticeably enlarges only after an intercurrent upper respiratory tract infection (infection or inflammation within the cyst). Secondary infection can produce pain, erythema, and, in more severe cases, abscess formation.
• Second branchial cleft anomalies present as a mass, sinus, or fistula tract along the anterior border of the sternocleidomastoid muscle. A sinus or fistula tract characteristically discharges mucoid material and sometimes becomes apparent only after secondary infection.
• A branchial cleft cyst without a sinus tract typically presents as a painless, fluctuant mass. It may similarly enlarge or become symptomatic after an intercurrent infection.
• Dermoid cysts present as a slow growing, midline neck mass, typically submental, with a soft, doughy consistency. They characteristically do not move with tongue protrusion, which distinguishes them clinically from thyroglossal duct cyst.
• Vascular and lymphatic malformations (the latter historically termed cystic hygroma when in the characteristic cervical location) vary with the type and extent of the malformation. They range from a soft, compressible, sometimes transilluminating mass (particularly macrocystic lymphatic malformation) to more complex, infiltrative lesions.
• These malformations are sometimes present at birth or apparent shortly after. They occasionally grow disproportionately or become symptomatic during periods of rapid growth, after intercurrent infection or, in some vascular malformations, with hormonal change.

• Ultrasound is a valuable, first line, non-invasive investigation for any congenital neck mass. It shows location, cystic versus solid nature, and relationship to surrounding structures.
• For suspected thyroglossal duct cyst, ultrasound critically shows whether normal thyroid tissue is present in its expected position. This matters because of the risk of removing ectopic, functioning thyroid tissue mistaken for a thyroglossal duct cyst.
• Perform thyroid function testing before any planned surgery for a suspected thyroglossal duct cyst. Existing hypothyroidism may suggest the mass is the patient's sole functioning thyroid tissue. This warrants particular caution and, potentially, nuclear medicine thyroid scanning before excision.
• Magnetic resonance imaging offers superior soft tissue characterisation. It may be indicated for larger, more complex masses, where more detailed delineation is needed for surgical planning, or where the diagnosis remains uncertain after ultrasound.
• It is particularly relevant for suspected branchial cleft anomalies, where precise characterisation of any sinus or fistula tract matters for surgical planning.
• Fine needle aspiration is generally neither required nor particularly informative for straightforward, characteristic congenital neck masses. The diagnosis is usually established from the clinical presentation and imaging.
• It may occasionally be considered where the diagnosis is genuinely uncertain or malignancy is a specific consideration, particularly in an older patient or with an atypical presentation.

• Thyroglossal duct cyst is treated with surgical excision (the Sistrunk procedure). This excises the cyst together with the central portion of the hyoid bone and a core of tissue extending up toward the tongue base along the thyroglossal tract.
• Simple cyst excision alone has a substantially higher recurrence rate. Excising the entire embryological tract is the key surgical principle for durable treatment.
• Acute infection or abscess in a thyroglossal duct cyst is managed initially with antibiotics and, where a discrete abscess has formed, incision and drainage. Definitive excision (Sistrunk procedure) is generally deferred until the acute process has settled, because of increased surgical complexity and risk of incomplete excision during active infection.
• Branchial cleft anomalies are treated with complete surgical excision of the cyst, sinus, or fistula tract. Complete excision minimises recurrence.
• Meticulous technique is required because of the close relationship to important neurovascular structures. For second branchial cleft anomalies this includes the carotid sheath and, in some cases, the facial nerve or its branches, depending on the tract course.
• Acute infection of a branchial cleft anomaly is similarly managed initially with antibiotics and drainage of any abscess. Definitive excision is generally deferred until the acute infection has resolved, as for thyroglossal duct cyst.
• Dermoid cysts are managed with surgical excision. This is generally more straightforward than for thyroglossal duct cyst, as there is no embryological tract needing additional excision.
• Vascular and lymphatic malformations need individualised management according to type, size, and location. Options range from observation for small, asymptomatic, stable lesions, through sclerotherapy (particularly effective for macrocystic lymphatic malformations), to surgical excision or debulking for more extensive or symptomatic lesions.
• Coordinate management through a specialist multidisciplinary vascular anomalies service, given the complexity and heterogeneity of these lesions.
• Follow up regularly for signs of recurrence after surgery. For thyroglossal duct cyst, monitor thyroid function postoperatively where there was any preoperative concern that the cyst might be ectopic, functioning thyroid tissue.