Endocrine Abstracts

Introduction

Ectopic thyroid tissue is a rare clinical entity, with a prevalence of 1: 300 000 in the general population. The ectopic tissue may be located anywhere from the base of the tongue to the diaphragm, the most frequent sites being lingual, thyroglossal, laryngotracheal, and lateral cervical regions. It may also occur in less frequent sites such as the esophagus, mediastinum, heart, adrenal glands, and pancreas. The mediastinum is the most frequent location after the neck. Malignant transformation of ectopic thyroid is uncommon; but even rarer is the development of papillary carcinoma in it. We report the case of papillary carcinoma arising in retrosternal ectopic thyroid tissue in association with an oncocytic variant of papillary carcinoma arising from the thyroid gland.

Case

A 50 years old female patient was presented to the medical consultation with 6 months history of neck swelling. Her medical and family histories were non-specific. The physical examination found a slight anterior cervical painless swelling. The neck ultrasonography was performed revealed 2 nodules of 4×9 mm and 4×3 mm classified Tirads 5. Besides, a nodule of 4 cm in size was identified in the superior mediastinum on the right. The USG-guided fine needle aspiration cytology performed on the retrosternal mass was reported to be in favor of ectopic thyroid tissue with malignant nature. Thyroid functional tests, calcitonin, and thyroid antibodies were within normal limits. A total thyroidectomy was scheduled for the patient. During the surgical exploration, the retrosternal ectopic thyroid mass of 4 cm was identified and removed. The histopathological examination was in favor of a retrosternal ectopic papillary thyroid carcinoma and a multifocal oncocytic variant of papillary carcinoma arising from the thyroid gland. The patient then underwent radioiodine ablation therapy (100 mCi) and was put on Levothyroxine suppression therapy.

Discussion and conclusion

Ectopic thyroid tissue results from abnormal embryologic development and migration of the thyroid gland. True malignant transformation in ectopic thyroid tissue is extremely rare and is always diagnosed after surgical excision of the lesion by pathology examinations. There are well-documented cases of ectopic thyroid cancer while primary tumoral lesion occurs in the orthotopic thyroid as described in our case. 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 about these types of anomalies in the perioperative examinations.