Primary solitary fibrous tumor (STF) of the thyroid gland is a rare tumor encountered in middle-aged patients with equal sex distribution. The first three cases of primary SFT of the thyroid were reported in 1993 and since then, to the best of our knowledge, only 39 cases have been published in English literature.

Literature review based on a clinical case

We present the case of a 44-year-old woman who began a study for a left thyroid nodule that produced compression symptoms. Cervical ultrasound: 2x2.7x3.6 cm thyroid nodule ACR-TR4. PAAF: Bethesda II Left hemithyroidectomy is performed Pathology: mesenchymal neoplasm, formed mainly by spindle-shaped elements of eosinophilic cytoplasm. Positive for CD34, CD99, BCL-2 and STAT6. 3% proliferation rate. In the multidisciplinary committee of endocrine tumors, it is decided not to complete thyroidectomy and follow-up by medical oncology

Primary thyroid SFT is a rare mesenchymal spindle cell neoplasm. Patients usually present a slowgrowing cervical mass. Histological diagnosis of SFT can be difficult because thyroid spindle cell tumors are rarely encountered in day-today practice and because differential diagnosis includes numerous other spindle cell lesions. Immunohistochemistry is the only ancillary test that can differentiate SFT from other mimicking spindle cell lesions. A definitive diagnosis of SFT can be made if the tumor is STAT6 nuclear positive. Prognosis in thyroid SFT is favorable, but because cases with late recurrence and metastases were reported, long-term surveillance is required.