# Congenital Neck Masses in Children

## Overview
Congenital neck masses are among the most common surgical conditions encountered by the pediatric otolaryngologist. The differential diagnosis is guided by the anatomic location (midline vs. lateral, level within the neck) and clinical characteristics. The principal entities include thyroglossal duct cysts, branchial cleft anomalies, dermoid cysts, and lymphatic malformations. Accurate diagnosis and appropriate surgical management, including the Sistrunk procedure for thyroglossal duct cysts, are essential to minimize recurrence.

## General Approach

### Differential Diagnosis by Location
**Midline**: thyroglossal duct cyst (most common midline), dermoid cyst, ectopic thyroid, submental lymph node. **Lateral (anterior triangle)**: branchial cleft anomaly, lymphatic malformation, reactive lymphadenopathy, atypical mycobacterial infection, vascular malformation. **Lateral (posterior triangle)**: lymphatic malformation (cystic hygroma), lipoma, brachial plexus tumor.

### Imaging
**Ultrasound**: first-line; characterizes cystic vs. solid, relationship to surrounding structures, thyroid gland assessment. **MRI**: best for defining extent of lymphatic malformations and relationship to neurovascular structures; no radiation. **CT with contrast**: for deep lesions, preoperative planning, or when infection/abscess is suspected. **Thyroid scan (Tc-99m)**: if ectopic thyroid is suspected (midline mass, no thyroid seen on ultrasound).

### Key Principles
Always confirm a normal thyroid gland is present before excising a midline neck mass. Fine-needle aspiration is rarely needed in children; imaging is usually sufficient. Timing of surgery: typically elective after age 1-2 years unless complications arise (infection, airway compromise).

## Thyroglossal Duct Cyst

### Embryology
Thyroid gland descends from the foramen cecum (base of tongue) to its final pretracheal position during weeks 3-7 of gestation. Thyroglossal duct normally obliterates by week 10. Persistence of any portion of the duct creates a cyst or sinus.

### Clinical Features
Most common congenital cervical mass (70% of congenital midline neck masses). Presents as a smooth, midline or paramedian neck mass, Located at or below the hyoid bone in 80% of cases. Characteristic: elevates with tongue protrusion and swallowing. May become infected (first presentation in some cases), enlarging and becoming tender. 1% risk of malignancy (papillary thyroid carcinoma) -- higher in adults.

### Diagnosis
Ultrasound: confirms cystic nature; evaluate thyroid gland (ensure orthotopic thyroid is present). If no thyroid gland visualized on US: thyroid scan to rule out ectopic thyroid (the "midline mass" may be the patient's only thyroid tissue). CT/MRI: for recurrent or complex cases.

### Surgical Management: Sistrunk Procedure
**Standard excision alone** has recurrence rates of 35-70%. **Sistrunk procedure** reduces recurrence to 2-5%. Technique: Excise the cyst with a cuff of surrounding tissue. Follow the tract superiorly to the hyoid bone. Excise the central body of the hyoid bone (key step). Follow the tract superior to the hyoid through the base of tongue musculature to the foramen cecum. Core of tissue at the tongue base is excised en bloc. Must excise the central hyoid: thyroglossal duct remnants pass through or are intimately associated with the hyoid body. If infected at presentation: antibiotics first, then elective Sistrunk 6-8 weeks after resolution (avoid surgery in acute infection if possible; some advocate incision and drainage followed by delayed Sistrunk).

## Branchial Cleft Anomalies

### Embryology
Six branchial arches develop during weeks 4-7; each has an external cleft (ectoderm), internal pouch (endoderm), and intervening mesoderm. Incomplete obliteration results in cysts, sinuses, or fistulae.

### First Branchial Cleft Anomalies
**Rare** (1-8% of branchial anomalies). **Work classification**: Type I: ectodermal origin only (duplication of external auditory canal); cyst near the EAC. Type II: ectodermal and mesodermal origin; tract runs from the neck (submandibular triangle) to the EAC or concha; intimate relationship with the facial nerve. Surgical excision requires identification and preservation of the facial nerve (parotidectomy approach often necessary).

### Second Branchial Cleft Anomalies
**Most common** branchial anomaly (90-95%). Cyst: smooth mass at the anterior border of the sternocleidomastoid, at the junction of the upper and middle third. Fistula: external opening at the anterior SCM border; internal opening at the tonsillar fossa. Tract courses between the internal and external carotid arteries, over CN XII and CN IX.

| Branchial Cleft | Frequency | External Opening | Internal Opening | Key Surgical Relationship |
|-----------------|-----------|-----------------|-----------------|--------------------------|
| First | 1-8% | EAC/preauricular | EAC/concha | Facial nerve (CN VII) |
| Second | 90-95% | Anterior SCM border | Tonsillar fossa | Between ICA and ECA; over CN XII |
| Third | Rare (left side) | Lower anterior neck | Piriform sinus | Over superior laryngeal nerve |
| Fourth | Very rare (left) | Lower neck/thyroid | Piriform sinus apex | Loops around aortic arch (left)  |  **Bailey classification** (cysts): Type I: superficial to SCM. Type II: deep to SCM, lateral to carotid sheath. Type III: between internal and external carotid arteries. Type IV: medial to carotid, adjacent to pharynx. Treatment: complete surgical excision including the tract (stepladder incision may be needed for long fistula tracts). |

### Third Branchial Cleft Anomalies
Rare; left-sided predominance. Present as recurrent left-sided suppurative thyroiditis in children. Internal opening at the piriform sinus. Tract descends in the neck, posterior to the common carotid, over the superior laryngeal nerve. Treatment: excision of the tract; endoscopic cauterization of the piriform sinus opening is an alternative.

### Fourth Branchial Cleft Anomalies
Very rare; left-sided predominance, Present as recurrent neck abscesses or thyroid abscesses. Tract originates at the piriform sinus apex, courses inferiorly (loops around the aortic arch on the left or subclavian artery on the right), then ascends. Treatment: excision or endoscopic cauterization of the piriform sinus opening.

## Dermoid Cyst

### Features
Midline subcutaneous mass; most common location is submental or nasal. Doughy texture, non-mobile with swallowing or tongue protrusion (unlike thyroglossal duct cyst). Lined by keratinizing epithelium with skin appendages (hair follicles, sebaceous glands). No connection to the hyoid or foramen cecum. Treatment: simple excision; recurrence is rare.

### Nasal Dermoid
Presents at the nasal dorsum; may have a pit or hair, Must rule out intracranial extension (MRI) before excision, Excision may require an open rhinoplasty approach.

## Lymphatic Malformations (Cystic Hygroma)

### Pathophysiology
Congenital malformation of the lymphatic system. Failure of lymphatic sacs to communicate with the venous system. Do not involute spontaneously (unlike infantile hemangiomas). Grow proportionally with the child; may enlarge with infection or hemorrhage.

### Classification (de Serres)
**Stage I**: unilateral infrahyoid. **Stage II**: unilateral suprahyoid. **Stage III**: unilateral supra- and infrahyoid. **Stage IV**: bilateral suprahyoid. **Stage V**: bilateral supra- and infrahyoid. Higher stages have worse outcomes and more complications.

### Types
**Macrocystic**: large cysts (>2 cm); respond well to sclerotherapy. **Microcystic**: small cysts (<2 cm); poor response to sclerotherapy; surgical excision more often needed. **Mixed**: combination.

### Clinical Features
Soft, compressible, transilluminating neck mass, Most present at birth or within the first 2 years, Posterior triangle is the most common location, May extend into the mediastinum, axilla, or floor of mouth, Acute enlargement with URI or hemorrhage into the cyst. Airway compromise if floor of mouth or supraglottic involvement.

### Management
**Observation**: for small, asymptomatic lesions. **Sclerotherapy**: first-line for macrocystic lesions. Agents: OK-432 (picibanil), doxycycline, bleomycin, sodium tetradecyl sulfate. Injected into the cyst under ultrasound guidance. Response rate for macrocystic: 80-90%; microcystic: 30-40%. **Surgical excision**: for microcystic disease, failed sclerotherapy, or acute complications. Complete excision often impossible without sacrificing vital structures. Subtotal excision with observation of remnant. Recurrence rate: 10-50%. **Sirolimus (rapamycin)**: mTOR inhibitor; emerging medical therapy for complex or refractory lymphatic malformations. **Tracheotomy**: for significant airway compromise.

<image>Anatomic diagram showing the locations and courses of first through fourth branchial cleft anomaly tracts. Lateral view of the neck with the sternocleidomastoid partially transparent. First branchial cleft tract shown from the EAC/concha through the parotid gland with relationship to the facial nerve. Second branchial cleft tract from the anterior SCM border coursing between the internal and external carotid arteries, over CN XII, to the tonsillar fossa. Third branchial cleft tract from the piriform sinus coursing posterior to the common carotid, over the SLN. Fourth branchial cleft tract from the piriform sinus apex looping under the aortic arch (left) and ascending along the tracheoesophageal groove. Each tract is color-coded with the internal and external openings labeled.</image>

<image>Clinical and imaging comparison of common congenital neck masses. Four panels with clinical photographs and corresponding ultrasound or MRI images. Panel A: Thyroglossal duct cyst -- midline neck mass in a child elevating with tongue protrusion; ultrasound showing a well-circumscribed anechoic cyst anterior to the hyoid. Panel B: Second branchial cleft cyst -- lateral neck mass at the anterior border of the SCM; CT showing a well-defined cystic lesion deep to the SCM and lateral to the carotid sheath. Panel C: Dermoid cyst -- submental midline mass; ultrasound showing a heterogeneous cystic mass with internal echoes. Panel D: Lymphatic malformation -- large, soft, transilluminating posterolateral neck mass; MRI (T2) showing a multiloculated hyperintense macrocystic lesion in the posterior triangle extending into the mediastinum.</image>

<image>Sistrunk procedure surgical technique for thyroglossal duct cyst. Step-by-step illustration showing: (1) Horizontal skin incision over the cyst. (2) Dissection of the cyst with a cuff of surrounding strap muscle tissue. (3) Following the tract superiorly to the hyoid bone. (4) Excision of the central body of the hyoid bone with bone-cutting forceps. (5) Following the suprahyoid tract through the base of tongue musculature to the foramen cecum region. (6) En bloc removal of the cyst, central hyoid, and core of tongue base tissue. An inset shows the sagittal anatomy with the thyroglossal duct course from the foramen cecum through the hyoid to the pretracheal position.</image>

## Clinical Pearls
Before excising any midline pediatric neck mass, always confirm that a normal orthotopic thyroid gland is present on ultrasound; if no thyroid is seen, obtain a thyroid scan to rule out ectopic thyroid as the only functioning thyroid tissue. The Sistrunk procedure (excision of the cyst, central hyoid body, and suprahyoid tract to the foramen cecum) is mandatory for thyroglossal duct cysts; simple cyst excision alone has an unacceptable recurrence rate of 35-70%. Second branchial cleft cysts are the most common branchial anomaly; the tract passes between the internal and external carotid arteries, a critical relationship during surgical excision. Recurrent left-sided neck abscess or suppurative thyroiditis in a child should raise suspicion for a third or fourth branchial cleft anomaly with a sinus tract opening at the piriform sinus. Macrocystic lymphatic malformations respond well to sclerotherapy (80-90% response rate); microcystic lesions are better managed surgically. Lymphatic malformations do not involute spontaneously (unlike infantile hemangiomas); expectant management is appropriate for small asymptomatic lesions, but growing or symptomatic lesions require intervention.

## References
- Foley DS, Fallat ME. "Thyroglossal duct and other congenital midline cervical anomalies." *Semin Pediatr Surg*. 2006;15(2):70-75.
- Prosser JD, Myer CM. "Branchial cleft anomalies and thymic cysts." *Otolaryngol Clin North Am*. 2015;48(1):1-14.
- Perkins JA, Manning SC, Tempero RM, et al. "Lymphatic malformations: review of current treatment." *Otolaryngol Head Neck Surg*. 2010;142(6):795-803.
- Sistrunk WE. "The surgical treatment of cysts of the thyroglossal tract." *Ann Surg*. 1920;71(2):121-122.