The fourth branchial cleft anomaly.

The fourth branchial cleft anomaly has long been postulated. A case in which a lower neck sinus tract extended under the clavicle near the subclavian vessels is presented. The distinguishing features of bronchogenic and branchogenic anomalies are discussed. It appears that unless a complication (e.g., abscess, inflammatory process) of the fourth branchial cleft sinus tract occurs within the mediastinum, mandating full exploration, the complete form of the anomaly may continue to remain undocumented.