Multiple branchial cleft-like cysts in Hashimoto's thyroiditis.

We report two cases of multiple intrathyroidal cysts in women with Hashimoto's thyroiditis. The cysts were lined by squamous and focally columnar epithelium, and they were surrounded by follicular lymphoid tissue and a fibrous capsule. They appeared similar to branchial cleft cysts of the lateral neck and were distinct from previously reported types of thyroid cysts. Although the histogenesis of these lesions is unclear, they are probably derived from developmental rests. A relationship between the cystic enlargement of these rests and the Hashimoto's disease seems likely.