A case of suspected ectopic thyroid cancer originating from the lateral thyroid primordium

Abstract

Ectopic thyroid gland is an embryological abnormality in which thyroid tissue is present outside the appropriate location of the thyroid gland, often occurring in the midline of the neck. We report a case of suspected ectopic thyroid cancer originating from the lateral thyroid primordium and arising in the lateral neck. The patient was a man in his 60s who was aware of a right neck tumor that had been gradually enlarging for half a year. At the first visit to our hospital, he had a cystic mass in his right neck. Fine-needle aspiration cytology raised the suspicion of metastasis of adenocarcinoma of unknown primary. However, we subsequently performed lumpectomy and diagnosed papillary thyroid carcinoma. This mass was cystic; however, although it was huge for lymph node metastasis, it was single a single mass of unknown origin because no lymph node structure was seen. Since the patient was at high risk of postoperative recurrence, we judged that internal radioactive iodine therapy was appropriate and performed total thyroidectomy and D1 dissection. Postoperative pathological examination revealed papillary carcinoma in both lobes and no lymph node metastasis. Postoperatively, he received radioactive iodine therapy and is currently under observation.