Uncommon thyroglossal duct cyst with inward tendency: a recommendation regarding ingrowth type.

Objective: There has been a growing number of case reports on uncommon thyroglossal duct cyst (TDC) extending into the oropharynx and/or laryngopharynx, which has often been misdiagnosed. We therefore examined the unfamiliar radiological and clinical characteristics of the cases in question so that we could advance the current store of knowledge.

Methods: From January 2005 to May 2009, all cases with TDC seen at a tertiary hospital, whose clinical data and images included CT and MRI, were included in this retrospective study. Cases with an uncommon thyroglossal duct cyst were chosen and divided to three different sub-types: intra-laryngeal, intra-lingual, and trans-laryngeal, according to the clinical syndrome and the sites of masses.

Results: In this study, 250 cases with TDC were collected, 21 (8.40%) of which presented extending images. Five such cases were of the intra-laryngeal type, with a mass lying close to the foramen cecum or posterior of the hyoid bone; 2 were classified as intra-lingual type, with a cyst in the tongue; 14 were classified as trans-laryngeal type, with a tumor occurring below the hyoid bone.

Conclusion: Uncommon TDCs tend to extend into the range of the respiratory tract. This novel type of ingrowth could facilitate early correct diagnosis and the formulation of an appropriate treatment plan.