Solitary fibrous tumor of thyroid: Case report

Summary

Solitary fibrous tumour is a relatively rare soft tissue fibroblastic tumour, accounting for approximately 2% of soft tissue tumours. It has been described primarily as a tumour of the pleural cavity; however, up to 70% of cases occur elsewhere, in any anatomical location, which can make diagnosis difficult. If this is the diagnosis being considered, the STAT6 antibody is currently available with high sensitivity and specificity. In this paper we describe the case of a 72-year-old female patient, followed up and treated by an outpatient endocrinologist for a multinodular euthyroid goitre for several years. Due to complete nodular remodelling of the left lobe of the thyroid gland and sonographic findings of several small nodules in the right lobe of the thyroid gland, total thyroidectomy was recommended to the patient. The operation was performed at the ENT department in Jindřichův Hradec Hospital. Material from the operation was subsequently sent for histopathological examination. Several hyperplastic colloid nodules and a small oncocytic adenoma were detected microscopically in the right lobe of the thyroid gland. In the left lobe, an imprecisely delineated, greyish-white lesion measuring 2 x 1.8 x 1.5 cm was observed on the section. Microscopically, the tumour consisted of spindle-shaped cells in a focally hyalinised stroma. In the immunohistochemical examination, tumour cells reacted positively with the CD34 antibody, and negatively with antibodies against thyroglobulin, cytokeratins (CK AE1/AE3) and S100 protein. Further immunohistochemical examinations (Bcl2, CD99, STAT6) with positive results were supplemented upon consultation at a higher facility. Based on morphology and the results of the immunohistochemical examinations, the tumour was diagnosed as a solitary fibrous tumour of the thyroid gland. This is a relatively unusual finding in this location; according to literature, only a few dozen cases have been described.

Keywords:

thyroid gland – solitary fibrosis tumor – SFT extrapleural – STAT6