Could Riedel's thyroiditis be subacute thyroiditis? A case report.

Our purpose in this paper is to make a case for the need to question whether Riedel's thyroiditis is in fact a rare variety of subacute thyroiditis. Total thyroidectomy was performed on a patient with a huge thyroid mass. The histopathological diagnosis was Riedel's thyroiditis with classical lymphoplasmacytic infiltration destroying thyroid tissue and invading perithyroidal soft tissue. However, in addition, histopathology showed epithelioid granulomas containing multinuclear giant cells. The existence of these giant cells led us to place this case somewhere between Hashimoto's thyroiditis and subacute thyroiditis (de Quervain's). Since giant cells are seen in the histopathology of subacute thyroiditis, we propose that the possibility of Riedel's thyroiditis being a form of subacute thyroiditis be observed and studied.