Unveiling the Rarity: A Case Report on Solitary Fibrous Tumor of the Thyroid Gland

Abstract

Solitary Fibrous Tumor (SFT) rarely manifests within the thyroid gland, an organ predominantly associated with epithelial carcinomas. This case report explores the clinical narrative of a 70-year-old patient presenting with a sizable SFT localized in the left lobe of the thyroid, posing diagnostic challenges uncommon in thyroid nodules. The report delves into the clinical history, radiological findings, pathological assessments, and therapeutic interventions, contributing to the limited literature on thyroidal SFTs. The patient's ultrasound revealed a substantial thyroid mass causing tracheal and vascular displacement, categorized as TIRADS 3. Fine needle aspiration indicated mesenchymal origin, prompting further investigation. Contrast-enhanced computed tomography depicted a well-defined lesion with varied enhancement, compressing surrounding structures. Histopathology confirmed a spindle cell proliferation, prompting immunohistochemistry revealing CD34, STAT6, and Bcl-2 positivity, aligning with SFT characteristics. The rarity of thyroidal SFTs poses diagnostic challenges, necessitating reliance on immunohistochemistry for accurate differentiation from other spindle cell neoplasms. Radiological investigations, including ultrasound and magnetic resonance imaging, contribute to preoperative planning. The case underscores the importance of meticulous pathological examination, emphasizing the utility of immunohistochemistry in confirming SFT diagnosis. The report enhances understanding among clinicians, pathologists, and researchers, guiding improved diagnostic accuracy and tailored treatment strategies for future occurrences of thyroidal SFTs.

Keywords: CD34; Extrapleural; STAT6; Solitary fibrous tumor; Thyroid.

Fig. 1

Fine needle aspiration cytological findings from the thyroid swelling. a–d Giemsa and Papanicolaou stained smears examined show scattered cellular fragments of mesenchymal cells which are spindle to oval-shaped with slightly wavy vesicular nuclei, ill-defined borders and moderate cytoplasm. [x100, x400]

Fig. 2

Radiological findings of the case. a–b Computed tomography of neck and chest showed a large well-defined hypodense lesion measuring 12.4 × 13 × 12 cm seen epicentred in the left lobe of the thyroid with heterogeneous enhancement

Fig. 3

Gross and histopathological findings.  a Gross examination revealed a firm grey-white tumor almost completely replacing the thyroid gland.  b Sections examined exhibited a spindle cell tumor with peripherally compressed thyroid follicles. [Hematoxylin and eosin, x100]. c–d  Sections examined show a cellular tumor comprising of patternless proliferation of spindle cells with ectatic vessels. The spindle cells are bland with ovoid elongated nuclei and scant cytoplasm. There was no cellular pleomorphism, necrosis or increased mitotic activity. [Hematoxylin and eosin, x400].  e–h Immunohistochemical examination revealed positive expression for CD34 (e), bcl2 (f) and STAT6 (g) and negative expression for calcitonin (h)