Fourth branchial cleft cyst presenting as a mediastinal mass in a neonate: a case report

Fourth branchial cleft anomalies are a rare congenital condition with varying presentations. Pediatricians and pediatric subspecialists must be familiar with this entity. A 4-day old term female presented with increased work of breathing. Exam was notable for intermittent subcostal retractions. X-ray showed a mediastinal shadow. Chest CT showed a large mass extending from the neck into the mediastinum. Interventional radiology placed a pigtail into the mass via the left neck. This drained milky cloudy fluid for seven weeks. After transfer to a quaternary children's hospital, an MRI showed a persistent large thick-walled cyst tracking into the neck. Laryngoscopy, bronchoscopy and esophagoscopy initially didn't show anomalies. Methylene blue dye was injected into the drain and seen to exit from a left pyriform sinus tract. This was confirmed with on-table fluoroscopy. Two days later, she underwent injection of sclerosing agents and contrast via the drain under fluoroscopy. The sinus tract was cauterized and suture ligated using laryngoscopy. Laryngoscopy a few days later revealed no patent sinus tract. Sclerosant was again injected. Ultrasound after one month showed a slightly decreased mediastinal mass. Ultrasound three months later was significantly decreased size. At 7-month follow-up, the patient remains asymptomatic, feeding and growing well. Fourth branchial anomalies are rare but must be considered in a pediatric patient of any age presenting with a neck or mediastinal mass.