[Solitary fibrous tumor in a thyroid follicular adenoma].

A 28-year-old female patient developed a 5.5 cm progressive thyroid nodule that was surgically removed due to local symptoms. Histologically, a solitary fibrous tumor (SFT) in a thyroid adenoma was diagnosed. The tumor had a specific NAB2-STAT6 fusion.Solitary fibrous tumors rarely occur in the thyroid gland and are described as both primary and secondary manifestations. The diagnosis, prognosis assessment and treatment decision are carried out analogously to SFT of other localizations.