Aberrant thyroid tissue can be found anywhere along the normal path of development and descent of the thyroid gland, from the foramen caecum down to the anterior mediastinum
Undescended thyroid can lead to a lingual thyroid gland near the base of the foramen caecum - often associated with inadequate thyroid hormone production, with subsequent goitrous enlargement, which can create local compressive symptoms in the upper neck
Can also occur along the path of the thyrothymic tract
Originates from the 3rd pharyngeal pouch and pulls along the inferior parathyroid glands and lower poles of the thyroid lobes along the descending path of the thymus gland
Foci of aberrant thyroid tissue along this path are referred to as 'thyroid rests'
Can occur in up to 50% of people, so not typically pathological, but can be mistaken for pathologic lymph nodes or parathyroid glands
Can connect to the thyroid proper by a thin stalk, or exist as separate structures
Intra-thoracic thyroid rests can enlarge to produce an intra-thoracic goitre
Treatment
Symptomatic lingual thyroid glands or thyroid rests can sometimes require excision
