Thyroglossal duct cysts and dermoid cysts both commonly present as midline neck lumps in children. They are treated as separate entities with different embryological origins. There are isolated reports of thyroid gland tissue in a dermoid cyst, concurrent thyroglossal and dermoid cysts, and cysts with mixed histology. It is not known if these are rare or common.

All children undergoing excision of a congenital midline neck cyst between January 2017 and December 2022 were identified. Histopathology slides were reviewed in detail.

In 53 children, there were 26 thyroglossal duct cysts, 24 dermoids, 1 lymph node and 2 with no diagnostic material identified. Five dermoids (28 per cent) had associated thyroid gland tissue, and 1 (4 per cent) had hybrid histology with keratinising and respiratory epithelium. Infection occurred in 17 per cent of dermoids prior to excision and 8 per cent of dermoids recurred after excision.

Hybrid histology, infection and recurrence are all common in midline neck dermoids. A new theory for their embryological origin is proposed, with the suggestion that some may need more extensive surgery.

Thyroglossal duct cysts and obstructive sleep apnoea are commonly occurring medical conditions which appear to present independently in patients. However, we noted three cases where the thyroglossal duct cysts influenced the development and/or therapy of obstructive sleep apnoea. In this article, these three case studies are presented, as is a study of the association between thyroglossal duct cysts and obstructive sleep apnoea, preceded by a literature review.

The patient in the first case study underwent hyoidthyroidpexia for obstructive sleep apnoea, which revealed an unexpected thyroglossal duct cyst. The second patient had previously undergone Sistrunk surgery for the removal of a thyroglossal duct cyst and subsequently presented with obstructive sleep apnoea. Finally, the third patient, who had previously undergone Sistrunk surgery, presented with obstructive sleep apnoea and underwent alternative surgery as hyoidthyroidpexia was no longer possible.

To our knowledge, the association between thyroglossal duct cysts and obstructive sleep apnoea has not been addressed previously. The results indicate that the relationship is much stronger than previously thought, and further research is required to investigate the extent of the association and possible causal relations.

To report a rare case of thyroglossal duct cyst carcinoma which presented with obstructive sleep apnoea, and to highlight the difficulties in making this clinical diagnosis.

Case report and review of the English language literature concerning thyroglossal duct cyst carcinoma.

Thyroglossal duct cyst carcinoma is a rare clinical entity found in only approximately 1 per cent of all patients operated upon for thyroglossal duct cyst. This condition usually presents in an identical manner to its benign counterpart; atypical presentations have not previously been reported. Our patient is the first reported case of a thyroglossal duct cyst carcinoma first presenting with symptoms of obstructive sleep apnoea, without a neck mass. Complete surgical excision with total thyroidectomy and lymph node clearance was performed, in view of the positive lymph node metastases (seen on imaging) and the need for post-operative radioiodine therapy.

Thyroglossal duct cyst carcinomas may present atypically, posing a diagnostic dilemma for the clinician. For patients diagnosed with obstructive sleep apnoea, it is imperative that a thorough otolaryngological examination be performed to exclude any underlying pathology.

We report an extremely rare case of the simultaneous occurrence of a thyroglossal duct cyst and a lingual thyroid in the absence of an orthotopic thyroid gland, in a seven-year-old girl from South India.

Case report and a review of the English language literature on the subject.

The patient presented with a mass on the tongue that had been present for three years, and an anterior neck swelling that had been present for two years. Examination revealed a midline, pinkish, firm mass present on the posterior one-third of the tongue. The neck showed a midline cystic swelling in the infrahyoid position. Radiological imaging confirmed the clinical findings, revealing the absence of her thyroid gland in the normal location. Sistrunk's procedure was performed leaving behind a lingual thyroid. At 13-month follow up, the patient was euthyroid with no recurrence.

To our knowledge the association of a lingual thyroid and a thyroglossal cyst has only been reported once in the literature. The presence of a lingual thyroid in the absence of a normally located thyroid gland or functioning thyroid tissue along the thyroglossal tract, confirmed by radionuclide and computed tomography imaging, may indicate the failure of the normal descent of the thyroid gland during embryonic development. This probable absence of the descent of the thyroid raises questions regarding the origin of thyroglossal duct cysts.

To review previous reports and to discuss the management of branching polycystic and giant thyroglossal duct cysts.

We present two cases of thyroglossal duct cyst: one a branching, polycystic thyroglossal duct cyst in an 11-year-old boy, and the other a giant thyroglossal cyst in a 41-year-old man. Such cysts are rare. Both patients were operated upon according to the methods of Sistrunk and Horisawa, and both had a satisfactory post-operative course.

We discuss the most important aspects of such cyst removal procedures.

Our experience suggests that surgery to remove an anomalous thyroglossal duct cyst should be performed using a technique based on the anatomy of the hyoid bone region.