Subacute granulomatous (De Quervain's) thyroiditis: Fine-needle aspiration cytology and ultrasonographic characteristics of 21 cases

Background: Subacute granulomatous thyroiditis (SGT) is an inflammatory disease that presents with different clinical and cytological characteristics. Although the diagnosis is generally made clinically, imaging methods and fine-needle aspiration (FNA) may provide assistance, particularly in atypical cases. The objective of this study is to reveal the ultrasonographic (USG) and cytological characteristics of SGT. Materials and Methods: The clinical, USG and cytological findings of 21 cases diagnosed with SGT were reviewed. Results: Ultrasonographic data was available in 20 cases. A hypoechoic thyroid nodule with irregular margins was detected in 12 of the 20 total cases. Of these, 9 cases complained about pain in the thyroid lodge and generally had unilateral lesions, heterogeneous and hypoechoic areas with indistinct margins, rather than nodular lesions, which were seen in 7 cases. Cytologically, the multinuclear giant cells (MNGCs) found in all cases were accompanied by a dirty background containing varying numbers of granulomatous structures, including isolated epithelioid histiocytes, proliferated/regenerated follicle epithelium cells and inflammatory cells and colloid. Conclusion: Though hypoechoic and heterogeneous areas with irregular margins are strongly associated with thyroiditis, SGT may also appear as painful or painless hypoechoic, solid nodules and generate challenges in differential diagnosis. Although the most remarkable characteristic observed in FNA cytology was the presence of multiple MNGCs with cytoplasm, a dirty background accompanied by mild-moderate cellularity, degenerated-proliferated follicular epithelium cells, rare epithelioid granulomas and mixed type inflammatory cells are characteristic for SGT. The assessment of these radiological and cytological findings in conjunction with clinical findings will assist in the achievement of an accurate diagnosis.