INTRATHYROIDAL LYMPHOEPITHELIAL CYST - A REPORT OF 2 CASES NOT ASSOCIATED WITH HASHIMOTOS-THYROIDITIS

Two cases of intrathyroidal lymphoepithelial cyst are described. Both of them were solitary, one being found incidentally in a patient opera ted on for a multinodular goiter, the other being clinically obvious a s a cold nodule. They exhibited features of cysts of branchial cleft o rigin, i.e. squamous cell lining epithelium and abundant lymphoid tiss ue with reactive germinal centers. The thyroid gland parenchyma showed a discrete lymphoid infiltration consistent with the diagnosis of foc al lymphocytic thyroiditis. In the first case a single epidermoid soli d cell nest was found. The histogenesis of intrathyroidal lymphoepithe lial cysts remains unclear, but their origin from cystically degenerat ed ultimobranchial body remnants (solid cell nests) seems to be most p robable. This assumption is supported by a similar immunohistochemical profile of solid cell nests and epithelial cells lining the cysts and also by the presence of one solid cell nest in the proximity to the c yst in one of our cases.