Endocrine Abstracts

Introduction: Solitary fibrous tumor (SFT) is a sporadic tumor, commonly found in the pleural cavity. It is like a large well-circumscribed mass, arising from mesenchymal tissue, with spindle cells proliferation, arranged in various patterns. SFT of the thyroid is exceptionally rare, with only about 28 cases being reported in the international literaterature.

A 34-year-old woman presented in the Department of Endocrinology with the diagnosis of a multinodular goiter. She had no clinical signs or symptoms at that moment. Biological and thyroid function tests were normal. We performed an ultrasonographic examination of the thyroid, which described a solid hypoechogenic nodule in the left lobe (12.13 ml); close imagistic surveillance was recommended. In the next presentations,we noticed the same euthyroid status but an increase in the nodule dimensions (4.9 × 5.5 × 3 cm) and compression symptoms. Fine needle aspiration biopsy (FNAB) under ultrasound guidation was performed with a favorable result after the Bethesda system. Duet o increasing in nodular size, a total thyroidectomy was done, and thyroid hormone replacement therapy was started. Immunohistochemistry revealed positivity for CD34 marker, CD99, BCL-2, CD 68, negativity for desmin and SMA, and a KI-67 index < 1%. The diagnosis was benign SFT arising from the thyroid gland. IGF-2 value was normal; the patient remains well 12 months after excision.

Discussions: Our case is a rare case of SFT of the thyroid, where the patient presented with an asymptomatic slowly increasing thyroid mass in the presence of a benign FNAB. There was no evidence of SFT before immunohistochemistry; the exam highlighted SFT characteristic features, very useful in the differential diagnosis that includes undifferentiated (anaplastic) carcinoma.

Keywords: solitary fibrous tumor, multinodulat goiter, thyroid tumor