Thyroid papillary carcinoma arising in ectopic thyroid tissue within a branchial cleft cyst.

Ectopic thyroid tissue comprises a rare clinical entity which can clinically manifest with the whole spectrum of thyroid disorders, including thyroid malignancy. Thyroid carcinoma arising in ectopic thyroid tissue is extremely rare, with only a few cases described in the literature so far. We present a very unusual case of a primary papillary thyroid carcinoma arising in a left lateral branchial cyst, describing our diagnostic and therapeutic approach for this uncommon clinical entity. This is the first case where recombinant thyrotropin was used along with radioiodine treatment in primary ectopic thyroid cancer.