Agenesis of Isthmus of Thyroid Gland in the Presence of Ectopic Thyroid Tissue Associated with Papillary Carcinoma.

The thyroid is an endocrine gland composed of two lateral lobes connected by a strip of thyroid tissue called an isthmus. The thyroid gland is usually associated with extensive morphological variations and developmental anomalies. During the 4th intrauterine week, the thyroid gland begins to develop mainly from the invagination of the endodermal cells of the ventral floor of the primitive pharynx. One of the anomalies of the thyroid gland is the agenesis of the isthmus of the thyroid. It is a rare condition and very few cases have been reported in the literature. Another rare developmental abnormality is the presence of ectopic thyroid tissues, which are characterised by the presence of thyroid tissue in locations other than the anterolateral region of the second and fourth tracheal cartilages. Ectopic thyroid tissues are most commonly found in the lingual region but are also found in the other head/neck localisations as well. In this present case report, a 54-year-old female patient with the agenesis of the isthmus of the thyroid gland with accompanying tissues of multifocal and multicentric papillary thyroid carcinoma will be discussed. When an agenesis of the isthmus of the thyroid is detected, the agenesis of the thyroid lobes or the presence of an ectopic thyroid tissue must be considered. Especially in the patients who will undergo a thyroid surgery, it should not be forgotten that the identification of an agenesis of the isthmus as well as the other thyroid anomalies during the preoperative examination, will make a remarkable contribution in deciding the strategy of the surgery and will help in preventing the development of surgical complications. However, it is not always possible to detect the presence of these anomalies, during the preoperative examinations of the patients who will undergo thyroid surgeries; therefore, one must be careful with regard to these type of anomalies in the perioperative examinations. To the best of authors' information, the present case is considered to be the first in the literature in English, presenting with an agenesis of the isthmus of the thyroid gland in the presence of ectopic thyroid tissues associated with papillary carcinoma.