MRI of the neck in a 45-year-old with painless neck mass shows a well-defined, thin-walled cystic lesion at the angle of the mandible anterior to the sternocleidomastoid muscle, posterior to the submandibular gland, displacing the carotid vessels medially. It has T2 bright homogeneous signal and no solid components. The most likely diagnosis is:

• A Cystic lymph node metastasis from oropharyngeal SCC
• B Thyroglossal duct cyst
• C Second branchial cleft cyst (type II) ✓
• D Carotid body tumour

Explanation

Second branchial cleft cysts (the most common branchial cleft anomaly, ~95%) classically present as well-defined thin-walled cystic lesions at the angle of the mandible, anterior to the SCM, lateral to the carotid vessels, and posterior to the submandibular gland — the 'Bailey type II' location. Cystic metastatic nodes from oropharyngeal HPV+ SCC appear similar but show irregular walls/septations and the primary tumour should be sought. Thyroglossal cysts are midline/paramedian at the hyoid. Carotid body tumour is solid and splays the carotids.

Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.