Congenital masses

Common congenital neck masses include thyroglossal duct cyst, branchial cyst, cystic hygroma, teratoma (mostly in infants) and haemangioma.

Thyroglossal duct cyst

The thyroglossal duct cyst originates from the epithelial remnants of the thyroglossal tract and therefore is typically located in the midline between the isthmus of the thyroid gland and the foramen caecum of the tongue base. It can be at, below or above, the level of the hyoid bone. The typical thyroglossal duct cyst moves with swallowing and protrusion of the tongue because of its adherence to the hyoid bone and adjacent strap muscles. It may or may not have a ductal connection to the tongue base. Ultrasound examination is useful in ruling out ectopic thyroid and in confirming the presence of a normal thyroid gland in the lower neck. Treatment is by Sistrunk's operation (excision of entire cyst with a small central segment of hyoid bone and any ductal connection to the tongue base). Small thyroglossal duct cysts with no history of infection can be observed as the risk of malignant change is well under 1%.

Branchial cyst

During the fifth embryonic week, the branchial apparatus, which is phylogenetically related to the primitive fill slits, develops into five paired mesodermic arches separated by four pairs of invaginations of ectoderm and endoderm known, respectively, as branchial clefts and pouches. Each branchial arch develops into cartilage, artery, nerve and muscles. Branchial anomalies in the form of a cyst, sinus (communicates to the viscera or skin) or fistula (communicates to both skin and viscera) can form from vestigial remnants of branchial pouches and clefts. Branchial anomalies are lined by squamous epithelium or respiratory epithelium or both. First branchial anomalies are rare and are of two types. A type I lesion is usually postauricular in location (commonly mistaken as postauricular sebaceous cyst) and represents a duplication of both membranous and cartilaginous portions of the EAC. A type II lesion typically presents as a cyst or sinus in the preauricular or upper neck with the fistula tract intimately related to the parotid gland and the facial nerve. Second branchial anomalies commonly present as a cyst in mid-neck (Fig. 20.19). It may course between the external and internal carotid artery and may reach the ton-sillar fossa. Third branchial lesions are uncommon. They present lower in the neck and may track posterior to the internal carotid artery to exit near the pyriform fossa. In children, an inflamed third branchial cyst may present clinically as acute thyroiditis. Differential diagnosis of a branchial cyst includes nodal metastasis of papillary carcinoma of thyroid or squamous carcinoma with cystic change and other inflammatory mass. Ultrasound examination and CT scan are useful to help differentiate branchial cyst anomalies from other conditions. Treatment of branchial anomalies is surgical excision. Surgical treatment of type II first branchial anomalies requires facial nerve dissection.

Figure 20.19. Large second branchial cyst.

Cystic hygroma

These are congenital malformations of lymphatic channels (lymphangioma) commonly occurring in the posterior neck. They are usually present at birth. They may be cystic or cavernous and the cavernous form tends to infiltrate diffusely adjacent tissues and structures. Surgical resection should be considered in childhood.

Teratomas and dermoid cysts

These are developmental cysts composed of trigeminal components foreign to the site of origin. In the head and neck region, true teratomas tend to arise from embryonic tissue near the primitive streak and notochord. According to Batsakis, teratomas include dermoid cyst and related cystic lesions (epidermoid or epidermal cyst, teratoid cyst and teratoma of the neck). Epidermoid cyst is lined by simple squamous epithelium, dermoid cyst is an epithelial-lined cavity with skin appendages, and teratoid cyst may contain squamous epithelium or ciliated respiratory epithelium. Dermoid cyst of the floor of the mouth may present in the midline submental area. Teratomas of the neck are commonly present at birth and the mass effect may be associated with respiratory distress and dysphagia. Therefore, surgical excision is always indicated. Malignant teratoma of the neck is rare.

Haemangioma

In the head and neck area, haemangioma typically present as diffuse, soft, subcutaneous masses that may gradually increase in size over many years. Unless localized, haemangioma is best treated conservatively once the diagnosis has been confirmed by ultrasound, CT scan or RBC scan. Haemangioma of skin (port-wine stain) can be treated by pulsed dye laser. Nodular or deep haemangioma can be treated by pulsed dye laser (585-590 nm) and/or long pulsed Nd: YAG laser (1064 nm) in multiple treatment sessions. Radiation should not be used for the treatment of haemangioma.

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