A Case of Ectopic Thyroid Tissue Diagnosed by Fine Needle Aspiration in the Lateral Neck

ABSTRACT

Ectopic thyroid glands generally occur in the midline as a result of abnormal median migration and their presence in lateral to the midline is rare. Embryologically, the thyroid gland is derived from two anlages a large median endodermal anlage and two lateral anlages. The median anlage produces most of the thyroid parenchyma, whereas the lateral anlage is derived from the fourth pharyngeal pouch and contributes 1-30% of the thyroid weight. In rare cases, failure of the lateral anlage to fuse with the median anlage can result in lateral ectopic thyroid gland. For many years, lateral, aberrant thyroid tissue in adults was a term used almost exclusively for metastatic thyroid carcinoma. However, aberrant, benign ectopic thyroid tissue rarely occurs. We present a 47-year-old man who had incidentally detected mass on the right lateral neck. He was clinically in a euthyroid status and the thyroid function test results were normal as well. Neck ultrasonography revealed a mild diffuse goiter and a 1.22 x 0.65 cm sized ovoid mass like lesion was located in the right level IV of the neck. The result of fine needle aspiration cytology was adenomatous goiter without lymphoid tissue or any malignancy. We rarely report aberrant, benign ectopic thyroid presence as a lateral neck mass.