Thymopharyngeal duct cyst: MR imaging of a third branchial arch anomaly in a neonate

Abstract

Third branchial arch anomalies are rare. The authors present a case report of a neonate with a rapidly growing neck mass due to cystic dilation of a persistent thymopharyngeal duct, which is a derivative of the third branchial arch. The presence of thyroid and thymic tissue in the cyst wall, the communication of the cyst with the piriform sinus, and the relationship of the cyst to carotid vessels and the sternomastoid muscle were consistent with the features of a thymopharyngeal duct cyst embedded in the thyroid gland.

Cervical Thymic Cyst in an Adult

“…Transverse cervical neck incision is the most common approach, although vertical approaches paralleling the anterior sternocleidomastoid border have been reported [15]. The excision of the mass should be performed with great care because of the close anatomical relationships of CTCs with large vessels and neck nerves (carotid artery, jugular vein, vagus nerve, glossopharyngeal nerve, hypoglossal nerve, phrenic nerve, and recurrent laryngeal nerve); particularly, if there is adherence of the CTC with those structures, CTCs may also present surgical challenges if the cyst extends into the mediastinum.…”

Thymopharyngeal Duct Cyst: A Case Presentation and Literature Review

“…Once the presence of normal thymic tissue is confirmed a transverse cervical neck incision is the most common approach, although vertical approaches paralleling the anterior sternocleidomastoid border have been reported. 7 For a suspected thymopharyngeal duct cyst the surgeon must be prepared to dissect along the carotid sheath and into the mediastinum. 5 A connection between the cyst and pharynx is often unknown pre-operatively despite appropriate imaging and laryngoscopy; therefore it is imperative intraoperatively to meticulously dissect out any fistula tracts as failure to do so can result in cyst recurrence.…”

“…However, in the ten cases reviewed, five cases were right-sided masses and at least three were female. 1,2,3,5,6,7,12 There can be associated findings of hoarseness, dysphagia, and stridor, especially in neonates. 5 Often, the cyst will appear and gradually enlarge following an indolent, painless course.…”

“…10 Air fluid levels within the cyst can indicate foregut communication. 7 The MRI shows low T1 signal and high T2 signal as well as superior soft tissue definition. 13 This study is particularly useful in imaging a fistula tract connecting to the pharynx as well as determining the relationship between the cyst and mediastinal thymus, an area in which the CT falls short.…”

“…5 A connection between the cyst and pharynx is often unknown pre-operatively despite appropriate imaging and laryngoscopy; therefore it is imperative intraoperatively to meticulously dissect out any fistula tracts as failure to do so can result in cyst recurrence. 7 Once resected, histologic analysis is crucial to confirm the suspected diagnosis.The majority of thymopharyngeal duct cysts have a multilocular structure. The cyst contents are highly variable ranging from clear to dark brown turbid fluid.…”