Multiple branchial cleft-like cysts in a female patient with Hashimoto's thyroiditis.

We report a case of branchial cleft-like cysts (intrathyroidal lymphoepithelial cysts) associated with Hashimoto's thyroiditis. Palpation did not detect any nodules. Multiple cystic lesions were detected in the lateral side of the thyroid bilateral lobes by imagings of an I-123 scintigram, Tl-201 scintigram, sonography, and computerized tomography. Sonography displayed multiple cysts with strong echogenic spots in the cystic fluid. Repeated fine needle aspiration biopsies of the cysts consistently revealed only normal lymphocytes. Although these lesions could not be given diagnosis, subtotal thyroidectomy leaving the intact isthmus was performed. Microscopic findings revealed multiple branchial cleft-like cysts lined by flattened epithelial cells. Surrounding the epithelial lining were dense lymphoid follicles with large, reactive germinal centers. The remaining thyroid parenchyma showed Hashimoto's thyroiditis. Multiple branchial cleft-like cysts should be considered when sonographic examination reveals multiple cysts in the lateral side of the bilateral lobes, and fine needle aspiration biopsy displays only normal lymphocytes. To our knowledge, this is the first case of branchial cleft-like cysts associated with Hashimoto's thyroiditis reported in Japan.