Fourth branchial pouch sinus: A diagnostic challenge

A fourth branchial pouch sinus should be included in the differential diagnosis of recurrent unilateral neck mass. The surgeon must have a high index of suspicion of this disorder and a thorough understanding of the embryology of branchial defects to diagnose this entity and to differentiate fourth branchial pouch sinus from other brachial defects. Radiographic evaluation may demonstrate a piriform sinus tract origin, but it does not differentiate a third arch tract from a fourth arch tract. Cannulation of the sinus tract by means of direct laryngoscopy before surgical excision aids in removal of the cyst and tract, circumventing recurrences. Surgical exploration is the only way to precisely differentiate a fourth branchial arch anomaly from a third arch anomaly. We suspect there are more fourth arch defects than reported in the literature and that the diagnosis is missed because the tract is never recognized or found.