On CT neck with contrast, a 3 cm well-defined cystic lesion is found at the anterior border of the sternocleidomastoid muscle at the level of the angle of the mandible. It displaces the SCM posteriorly and the carotid vessels medially. The MOST likely diagnosis is:

• A Reactive cervical lymph node
• B Cystic hygroma (lymphatic malformation)
• C Thyroglossal duct cyst
• D Second branchial cleft cyst ✓

Explanation

A second branchial cleft cyst classically presents as a well-defined unilocular cystic mass at the anterior border of the SCM at the angle of the mandible/upper neck, lateral to the carotid space — the level of the tonsillar fossa (second arch remnant tract). On CT, it is a thin-walled cystic lesion that displaces the SCM posteriorly and the carotid vessels medially. Thyroglossal duct cysts are midline, most commonly at or below the hyoid. Cystic hygromas are multilocular infiltrative lesions. Reactive nodes have a solid hilum.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.