Thyroglossal Duct Cyst

—Common Anatomical Pattern of the Thyroglossal Duct and Rationale Behind the Operative Concept—

Abstract

The Sistrunk operation for thyroglossal duct cyst (TGDC) is widely accepted as the method with the fewest recurrences. His operative concept is that all or as much as possible of the thyroglossal duct (TGD) should be removed. We already clarified the common anatomical pattern of the thyroglossal duct based on the following pathological studies. From the pathological study of specimens provided by Sistrunk operations in 81 cases in 1989-2010, we clarified the histological specificity and three-dimensional structure of the TGD. Thyroglossal duct remnants near the foramen cecum were also studied in 20 autopsy cases. The common anatomical pattern of the TGD is as follows. The cyst is usually located caudal to the hyoid bone mostly at the midline. The duct extends upwards from the cyst ventral to the hyoid bone, with many or a few branches and secretory glands. These ducts or branches merge into a single duct at the level of the cranial portion of the hyoid bone. However, as it leaves the hyoid bone and approaches the foramen cecum, many branches spread out from a single duct, which communicate with many secretory glands. Those spreading branches merge again into a single duct that continues to the foramen cecum. The epithelium of the TGD in the branched duct in tongue is usually ciliated epithelium that efficiently accelerates the secreted mucous flow to the foramen cecum. The TGD epithelium around the hyoid bone and below the hyoid bone usually does not have cilia, however, and is usually squamous or has defects. Secreted mucous thus stagnates below the hyoid bone level and a cyst or mass can easily develop. From the pathological and clinical studies of recurred cases, the suspected causes of recurrence included the following: 1) preoperative infection, 2) multiple TGD branches in the tongue, and 3) an unusually ectopic mucous gland draining into the main duct of TGD in cases with multiple recurrence.
The proposed operative concept is that poorly drained anatomic part (the hyoid and below the hyoid level) should be excised with the Sistrunk procedure using a shallow core out and 95-97% cases of TGDC will be cured with this procedure. When recurrence is encountered, the cause of recurrence must be multiple lingual branches of the TGD. In the second operation, total secreted mucous should decreased with a Sistrunk procedure using a deeper and wider core out. In a rare case, when the ectopic mucous gland is found to be the cause of multiple recurrences, it should be surgically excised.