Riedel's thyroiditis associated with follicular carcinoma

Riedel's thyroiditis is an uncommon disorder of unknown etiology that is ch aracterized by an invasive fibrotic process that partially destroys the gla nd and extends into adjacent neck structures. Its clinical manifestation as a stony-hard, poorly defined enlargement over the thyroid gland and local compression of the trachea, esophagus and recurrent laryngeal nerve can mim ic invasive thyroid carcinoma. Because Riedel's thyroiditis is a self-limit ing disease, its management should be conservative. However, invasive cance r such as follicular carcinoma can occur in association with Riedel's thyro iditis. Such a concurrence completely changes the focus of management. We r eport a case of Riedel's thyroiditis that was found in a patient with a fol licular carcinoma. The strategy of management is discussed together with a review of the relevant literature.