Fine-needle aspiration of Riedel's disease: report of a case and review of the literature.

The cytomorphological features of a case of Riedel's thyroiditis (Riedel's disease) in a 37-yr-old woman are reviewed. The patient presented with a diffusely enlarged thyroid gland with extension to carotid and jugular vessels bilaterally. A fine-needle aspiration of the right lobe of the thyroid demonstrated moderate cellularity with fragments of fibrous tissue with bland spindle-shaped cells and myofibroblasts. The patient subsequently underwent a bilateral subtotal thyroidectomy with removal of two-thirds of both lobes of the thyroid. A frozen section diagnosis of Riedel's disease was later confirmed on paraffin sections. Here we describe the cytological findings of a case of Riedel's disease and provide some helpful clues in distinguishing it from other forms of thyroiditis such as fibrosing variant of Hashimoto's thyroiditis, subacute thyroiditis, or granulomatous thyroiditis and from malignancy with which it can be confused both clinically and cytologically.