An Uncommon Thyroid Tumor: The Diagnostic Challenge of Solitary Fibrous Tumors.

Background

Solitary fibrous tumors are uncommon fibroblastic neoplasms. These tumors are characterized by the recurrent NAB2-STAT6 gene fusion, which is a hallmark of solitary fibrous tumors (SFTs), particularly those arising in the thoracic cavity. While SFTs are mostly found in the abdomen and pleura, they can occur in various locations, including the head and neck region (6% of cases of SFTs). Solitary fibrous tumors of the thyroid (SFTTs) are extremely rare, accounting for only 0.1% of all thyroid tumors. The gold standard imaging modality for thyroid tumors is ultrasonography, even though distinctive characteristics for these types of neoplasms are absent, making pre-operative diagnosis more challenging. Aim: The aim of this study is to perform a systematic literature review and to describe our case by analyzing the main clinical features, histological diagnostic features and treatments of this rare tumor, in order to clarify the behavior and molecular characteristics of SFTTs.

Methods

A comprehensive systematic literature review was conducted according to the PRISMA guidelines for SFTTs. We searched the PubMed and EMBASE databases for articles published up to November 2025. The inclusion criteria include confirmed diagnosis of SFTT, while articles describing unrelated neoplasms or articles that were not in English were excluded. A standardized form was used to extract information on the imaging characteristics, histological diagnosis, treatment and outcome.

Results

As of 2025, a total of 43 articles were selected, with 61 reported cases of SFTT in the English literature. Pre-operative diagnosis of SFTT is controversial and usually requires immunohistochemical confirmation. In our case, molecular analysis identified, for the first time, a NAB2ex6-STAT6ex17 fusion, contributing to the molecular characterization of this rare tumor.

Conclusions

SFTTs are rare and difficult to diagnose; thus, they require a multidisciplinary approach for accurate diagnosis and management. The combination of imaging, cytology, histopathology, and molecular testing is essential in distinguishing SFTTs from other thyroid malignancies. Surgical excision remains the mainstay of treatment, and long-term follow-up is recommended due to the potential risk of recurrence or metastasis.