Site:

Along the anterior border of sternomastoid usually in the region of the angle of jaw. There is a slight left-sided predominance.

Formation:

The cause is usually a  development abnormality  arising in the early prenatal period, typically failure of obliteration of the second, third, and fourth  branchial cleft, i.e. failure of fusion of the second branchial arches and epicardial ridge in lower part of the neck. The appendages of the ectodermal lined enclosed space (cervical sinus), sweat and sebaceous glands continue their secretions which gradually distends the space to form the cyst. If sinus tracts are present, they typically drain into the  tonsillar fossa, found between the  palatoglossal arch and the  palatopharyngeal arch.

Contents:

Tooth paste like material rich in cholesterol.

Clinical features:

1. Age: Late childhood and young adults M=F.
2. Branchial cleft cysts are often asymptomatic.
3. May be painful only if infected.
4. Characteristics of Branchial cyst:
   • Smooth, ovoid in size.
   • Fluctuation positive.
   • Transillumination negative.
   • Non compressible.
   • Non palpable cervical lymph nodes.

Pathology:

The cyst wall is composed of squamous epithelium (90%), columnar cells with or without cilia, or a mixture of both with lymphoid infiltrate, often with prominent germinal centers and few subcapsular lymph sinuses. Cholesterol crystals may be found in the fluid extracted from a branchial cyst.

Diagnostic Criteria:

1. Diagnosis of branchial cleft cysts are typically done clinically due to their relatively consistent location in the neck.
2. Cholesterol crystals present in aspirated material.

Relations of the Cyst:

Superficial to the Internal carotid, glossopharyngeal nerve, stylopharyngeus, muscle. (Structures derived from the third arch). Deep to the lesser cornu of the hyoid bone, stylohyoid ligament, posterior belly of digastric muscle, facial nerve and external carotid artery. (Structures derived from the third arch).

Treatment

• External and internal carotid arteries.
• Pharyngeal wall.
• Accessory and hypoglossal nerve.

Differential diagnosis:

• Tuberculous lymphadenitis.
• Reactive lymphadenopathy.
• Lymphoma.
• Nerve sheath tumor.
• In children, dermoid cyst or rhabdomyosarcoma should also be considered.