Follicular Variant of Papillary Carcinoma Arising From Lingual Thyroid With Orthotopic Hypoplasia of Thyroid Lobes

The human thyroid gland derives from a median anlage and 2 lateral anlagen. The development of the thyroid occurs during weeks 3 to 7 of embryologic development when the median anlage descends from the foramen cecum to its usual pretracheal location. Toward the end of the migration, the lateral anlagen dissociate from the caudal base of the fourth and fifth pharyngeal pouches to migrate medially and join the thyroid gland. This structure is called the ultimobranchial body, and it contributes the parafollicular cells (or C cells) and 1% to 30% of the thyroid weight. Failure of median anlage descent can result in ectopic deposition of thyroid tissue anywhere along the path of descent. The most common location for ectopia of the thyroid is the tongue base, known as lingual