Clinical presentation: a 31-year-old woman with fever and painful thyroid lasting for 5 weeks. She got three courses of antibiotics without any effect. She was referred for an evaluation with the suspicion of non-Hodgkin lymphoma.

Palpation: both thyroids were hard and painful.

Functional state: hyperthyroidism with TSH-level 0.01 mIU/L, FT4 46.1 pM/L, ESR: 65 mm/H.

Ultrasonography: a great part of the thyroid was composed of hypoechogenic areas with blurred borders. The vascularization was almost absent.

Cytological diagnosis: subacute, granulomatous de Quervain's thyroiditis.

Suggestion: steroid therapy.