Teenager with a left neck mass

CT of second branchial cleft cyst
Axial (above), coronal (below left), and sagittal (below right) CT with contrast of the neck show a thin walled low density mass anterior to the left sternocleidomastoid muscle and posterior to the left submandibular gland. Superiorly the mass goes to the angle of the mandible and inferiorly the mass goes to the hyoid bone.

The diagnosis was second branchial cleft cyst.