Ectopic Thyroid Tissue in the Adrenal Gland: A Case Report

Background. Ectopic thyroid tissue is a rare abnormality resulting from a developmental defect during the early stages of thyroid gland embryogenesis. It is usually found anywhere along the embryonic pathway of the thyroid anlage in the midline of the ventral pharynx, from the tongue to the trachea. It is difficult to explain ectopic thyroid tissue beneath the diaphragm from the perspective of embryonic evolution. A few cases of ectopic lesion have been reported in abdominal organs including adrenal glands. The current study describes a case of ectopic thyroid tissue in the adrenal gland. Case Presentation. We reported a case of ectopic thyroid tissue in the adrenal gland. A 48-year-old male, with history of hyperthyroidism many years ago who was in euthyroid state after treatment. He was diagnosed as having a right adrenal tumor about 4 cm in size during a health check-up. Routine laboratory studies including TSH, free T4, aldosterone, and renin showed normal results. The patient received laparoscopic adrenalectomy. Microscopically, the tumor was composed of normal adrenal tissue with a cystic lesion lined by a single layer of follicular cells which were thyroid transcription factor-1 positive. A diagnosis of ectopic thyroid tissue was reached. Conclusion. Ectopic thyroid tissue in the adrenal gland is rare and the pathogenesis remains unknown. Nevertheless, it should be taken into consideration in a non-functional adrenal mass.