A 68-year-old man had a rapidly growing, painless neck mass, thought to be nodular goiter. Ultrasonography showed a giant, heterogeneous mass occupying the middle and superior poles and protruding outside of the left thyroid lobe. The results of the thyroid function tests were normal. Thyroid scintigraphy revealed a large hypoactive nodule in the left thyroid lobe. Complete surgical removal of tumor was performed and macroscopically demonstrated a well-demarked lesion outside the thyroid gland. Microscopically, the lesion was composed of fibroblast-like spindle cells in a patternless architecture and extensive stromal hyalinization. Immunohistochemistry showed positive reaction for CD34 in spindle cells and diffuse bcl-2 staining. The pathology was confirmed as solitary fibrous tumor. In the follow-up period after surgery, thyroid scintigraphy showed normal left thyroid lobe. Solitary fibrous tumor originated from or associated with thyroid gland is extremely rare. According to our knowledge, this is the first reported solitary fibrous tumor presenting like a cold thyroid nodule. This pathology must be considered for differential diagnosis of neck masses in the thyroid region.
Solitary fibrous tumor (SFT) is a rare spindle cell neoplasm of mesenchymal origin that was first described in the pleura [
A 68-year-old man presented with a 2-month history of a rapidly growing mass in the left neck on the thyroid gland region. He did not have any history of thyroid disease. He did not describe any symptoms like hoarseness, dyspnea, local pain, or weight loss. In laboratory evaluation, thyroid function tests, serum calcium, phosphorus, and parathormone were all evaluated as normal ranges. Serum calcitonin was measured as <2 pg/mL, which is low. Thyroid ultrasound revealed a 5 mm isoechogenic nodule on the right lobe and an 8 cm in diameter hypoechogenic, heterogeneous giant mass with irregular margins that was thought to be a nonthyroidal mass compressing the thyroid left lobe or may be a mass originating from thyroid gland and protruding outside the gland (Figure
Ultrasonography showing a heterogeneously hypoechoic giant mass with undetermined inferior margins.
Cervical lymph nodes had normal appearance. Tc-99m scintigraphy of thyroid gland was evaluated as a cold nodule occupying the middle and the superior regions of the left lobe (Figure
Thyroid scintigraphy using
An ultrasound-guided fine-needle aspiration biopsy (FNAB) of the lesion was performed. It was reported as suspicious probable malign cytology such as medullary thyroid carcinoma. The magnetic resonance imaging (MRI) showed a huge amorphous, heterogeneous, expansive mass occupying the space from the left lobe of the thyroid gland to the retrotracheal area, which was
Magnetic resonance imaging scan showing heterogeneous mass in relation to the left thyroid lobe marked with an arrow.
The patient underwent surgery for exploration and tumor excision. Macroscopically, the tumor was well circumscribed and externally compressing the left thyroid lobe. As the mass was evaluated as distinct lesion from the thyroid gland intraoperatively, left thyroid lobectomy was not performed. Histology showed the tumor composed of spindle cells with patternless architecture and extensive stromal hyalinization (Figure
Patternless architecture and extensive stromal hyalinization (H&E ×200).
The lesion had a strong positive immunohistochemical reaction for CD34 in spindle cells (Figure
Diffuse CD34 staining in spindle cells (CD34 ×200).
Diffuse CD34 staining in stroma (CD34 ×200).
Diffuse bcl-2 staining (bcl-2 ×200).
The final pathological diagnosis was solitary fibrous tumor. There was no complication postoperatively. Nine months after resection, the patient was free of disease. Neck region was evaluated by ultrasound; the left lobe of thyroid was evaluated clearly. Postoperative thyroid scintigraphy showed increased focal uptake in the middle and superior poles of the left thyroid lobe (Figure
SFT is a rare tumor in adults. It was first described as a pleura-based neoplasm or localized pleural mesothelioma [
Symptoms of SFT in the neck are nonspecific and are related to general presence of a soft tissue mass in the area affected. They present nearly equally as asymptomatic, slowly enlarging masses or with local symptoms due to compression [
There are some difficulties in differentiating perithyroidal soft tissue tumor from a mass belonging to thyroid. It may be confused with thyroid nodule [
Thyroid SFT shows general benign clinical behavior. This data is in contrast to the outcome observed in patients with nonthyroidal SFT. Sung et al. reported malignancy rate as 30.2% for pleural SFTs [
Fine-needle aspiration biopsy is the gold standard method in differentiation of benign and malignant nodules in the thyroid gland [
All reported thyroid SFTs were histologically and immunohistochemically similar to benign SFTs in the pleura. Microscopically, they were composed of bland spindle fibroblast-like cells growing in patternless manner with variable amounts of intercellular collagen bundles, keloid-like hyalinization, and alternating hypercellular and hypocellular areas [
However, SFTs are generally considered to be benign neoplasm. Previous studies have demonstrated that 10–15% of intrathoracic SFTs were malignant [
Computed tomography (CT) and MRI are often utilized in the assessment of SFTs to better define their extension into nearby tissues and preoperative evaluation. Because SFTs have presented themselves as huge masses, these imaging methods can demonstrate tracheal deviation [
Imaging techniques like magnetic resonance, ultrasonography, and thyroid scintigraphy may be insufficient for the neck masses on thyroid gland localization in order to distinguish its origin. For these patients, final diagnosis can be made by multidisciplinary approaches including the surgery. SFT associated with thyroid gland is very rare. Up to date, most patients had a benign course, but also malignant SFT of the thyroid was reported. However, our patient did not have any malignancy criteria. We recommend careful and long-term followup as clinical behavior of this rare tumor is still undetermined.
Written informed consent was obtained from the patient for publication of this case report and any accompanying images. A copy of the written consent is available for review.
The authors declare that there is no conflict of interests regarding the publication of this paper.
Oya Topaloglu is the corresponding and primary author of this case report. Bekir Ucan, Taner Demirci, and Muyesser Sayki Arslan analysed and interpreted the patient’s data. The surgery was performed by Guleser Saylam. Pathology of the patient was evaluated by Evrim Onder. Images of nuclear medicine and radiology were analysed by Sinan Gultekin and Alper Dilli. Mustafa Sahin, Erman Cakal, Mustafa Ozbek, and Tuncay Delibasi were contributors for writing the paper’s discussion. All authors read and approved the final paper.