Branchial cleft cyst posterior to the carotid vessels.

Branchial cleft anomalies may appear as a sinus fistula or cyst. An understanding of the developmental embryology and anatomy can predict branchial cleft anomalies by the relationship of the corresponding branchial arches that form at the time of development. The second branchial cleft anomalies are the most common and may be found along a tract from the anterior border of the sternocleidomastoid muscle anterior to the carotid vessels and IX and XII. A cyst may form anywhere along this tract but most commonly is just lateral to the internal jugular vein anterior to the carotid vessels. We describe a patient with a second branchial cleft cyst that was posterior to the carotid vessels documented by computed tomography. The cyst was found intraoperatively to be clearly posterior to the common carotid artery. This case demonstrates the need for an understanding of developmental embryology, anatomical landmarks and variations.