Infected second branchial cleft cyst

Findings

There is a well circumscribed low attenuating, likely cystic, mass located posterior to the submandibular gland, lateral to the carotid space, and anteromedial to the sternocleidomastoid muscle. The mass demonstrates slight rim enhancement, with mild inflammation of the adjacent fat.

Differential diagnosis:
- Infected second branchial cleft cyst
- Necrotic malignant adenopathy
- Lymphangioma
- Thymic cyst


Diagnosis: Infected second branchial cleft cyst


Key points

Most common type of branchial cleft anomaly – accounts for 75% of branchial cleft anomaly in children and >90% in adults
Results from failure of obliteration of the cervical sinus
Usually not associated with other anomalies
Four subtypes depending on location: Bailey classification – type II is the "classic" location as described below
May have associated fistulas

Clinical Presentation:
- Presents as painless mass at the lateral aspect of the neck
- Mass may be chronic, and may become larger with respiratory infection
- May be painful if infected
- Age of presentation between 10 and 40 year old
- No sex or race predilection
- Treatment is complete surgical excision, with good prognosis
- Controversial if malignancy can arises from branchial remnant


Imaging

Usually a round or oval shaped cystic mass
Located at the anterior triangle or angle or mandible
Lateral to carotid space, posterior to the submandibular gland, and anteromedial to the sternocleidomastoid muscle
Variable in size, may be up to 10 cm

Contrast enhanced CT:
- Cystic density mass with non enhancing wall
- If infected, wall will be thicker and may enhance, with inflammation of adjacent soft tissues

MRI:
- Cystic mass isointense to fluid on T1 and T2
- May become hyperintense on T1 if infected
- Will demonstrate wall enhancement if infected