Ectopic thyroid gland resembling a thyroglossal duct cyst.

KEY CLINICAL MESSAGE: This rare diagnosis highlights the importance of anatomical and embryological knowledge in the differential diagnosis of neck masses.

ABSTRACT: A 41-year-old woman was referred to the head and neck surgery department because of a large midline neck mass at the level of the hyoid bone that was diagnostic for functioning thyroid tissue in a totally ectopic location.