Congenital neck masses are developmental anomalies that can manifest either at birth or later in life, usually following a respiratory infection. The most common congenital neck masses are thyroglossal duct cysts, branchial cleft cysts, and cystic hygromas. These malformations manifest as painless neck masses that, as they grow, can cause dysphagia, respiratory distress, and neck pain by compressing surrounding structures. The location of the mass depends on the embryological structure the cyst arises from. Diagnosis is based on clinical findings and imaging results (ultrasound, CT, MRI), which also help in surgical planning. Treatment consists of complete surgical resection to prevent recurrence and complications such as infection or abscess formation.
- Definition: a remnant of the thyroglossal duct, which forms during the embryonic development of the thyroid gland and normally regresses before birth
- Pathophysiology 
- Clinical features: The cyst is present from birth and is usually detected during early childhood.
- Neck and thyroid examination
- Ultrasound of the neck to evaluate the cyst and confirm the location of the thyroid
Contrast-enhanced CT of the neck: preferred imaging modality
- Thyroglossal duct cysts are demonstrated as well-defined lesions with homogenous fluid attenuation and surrounding rim enhancement, typically close to the hyoid bone.
- Allows for assessment of anatomical location, relation, and extent of the cyst as well as its relation to normal orthotopic thyroid tissue.
- TSH levels
- If an infection is suspected, fine needle aspiration should be performed for Gram stain and culture (including AFB and mycobacterial culture).
- Treatment 
- Complications 
- Definition: remnants of the embryological second branchial cleft or cervical sinus, which normally regresses before birth
- Pathophysiology: : formed due to incomplete obliteration of and pouches
- Clinical features: usually diagnosed in late childhood or in adulthood after a previously undiagnosed cyst becomes infected 
- Treatment: : complete surgical excision of both the cyst and any associated tracts 
- Complications: : infection of the cyst, tract, or sinus, with possible abscess formation
- Definition: a congenital lymphatic cyst (macrocystic lymphangioma) in the caused by malformation and obstruction of the fetal lymphatic system 
- Clinical features
- Prenatal ultrasound : fluid-filled neck mass with or without septations 
- Ultrasound to identify mass in infancy
- CT or MRI may be used to further assess anatomical structures for surgical planning.
- Prognosis: Recurrence is common following surgical excision of extensive hygromas.
The differential diagnoses listed here are not exhaustive.