Case of the Week

Update June 16, 2016: Portions of the Background and Differential Diagnoses sections have been updated to better highlight the importance of ruling out metastatic nodal disease when encountering cystic neck masses. Two additional references have also been added.

• Background:
  • Congenital branchial anomalies present in the form of cysts, sinuses, or fistulae. They arise from an incomplete obliteration of the cervical sinus of His of the branchial apparatus, or from buried cell rests.
  • Branchial cysts presenting in adults are rare, so a new cystic neck mass should be always considered first as a metastatic nodal disease. The radiologist should be aware that in nonsmoking patients under 40 years old the incidence of a necrotic metastatic lymph node mimicking a benign neck mass is higher.
• Clinical Presentation:
  • Neck swelling
  • Recurrent infections of the lesion
• Key Diagnostic Features:
  • Location and extent of the lesion from the tonsillar fossa to the lower two-thirds of the anterior border of the sternocleidomastoid muscle is characteristic of the tract of a 2nd branchial arch anomaly.
  • Cysts involving the entire tract are unusual.
• Differential Diagnoses:
  • Metastatic cystic/necrotic nodes: As mentioned above, this is the most common cause for a new neck mass in adults. The presence of any focal wall thickening or nodular wall enhancement should be carefully looked for. In this case, the extension from the tonsillar fossa and the course of the lesion passing between the ICA and ECA to the anterior border of the sternocleidomastoid muscle may aim to a brachial cleft cyst. Nevertheless, there are significant overlapping features between both entities, so a branchial cleft cyst in adults should be considered as a diagnosis of exclusion.
  • Abscessed lymph nodes: Usually will show a thick irregular enhancing wall with inflammatory changes around the nodal cystic lesion.
  • Cystic schwannoma: Elongated lesions with cystic component typically located in the carotid space (vagus nerve or sympathetic chain) or in the posterior cervical space (spinal nerve or brachial plexus). Extension in between ICA and ECA and to the subcutaneous plane in the present case is usually not seen in cystic schwannoma.
  • Lymphatic malformation: Thin-walled cystic lesion typically located in the posterior cervical space. Typically seen in children. Extension between ECA and ICA to tonsillar fossa region is unlikely in lymphatic malformation.
• Treatment:
  • Surgical excision