Solitary fibrous tumor of the thyroid gland

Cytopathology of solitary fibrous tumor: a series of 34 cases

INTRODUCTION

Solitary fibrous tumor (SFT), a fibroblastic neoplasm characterized by a specific genetic alteration (NAB2-STAT6 fusion) and relatively specific immunohistochemical profile (STAT6/CD34 positivity), is seldom the subject of cytopathology data. We report our experience with scrape smears and fine-needle aspiration (FNA) biopsies of SFT in a large patient cohort.

MATERIALS AND METHODS

A search was made of our cytopathology and surgical pathology databases for cases diagnosed as solitary fibrous tumor (SFT). FNA biopsy smears, imprint smears, and cell blocks were performed and examined using standard technique.

RESULTS

Thirty-four cases from 30 patients (M:F = 1.1:1; age range: 24-86 years, x = 58 years) met inclusion criteria for this study. All patients had prior or subsequent tissue confirmation of SFT. Twenty-seven (79%) specimens were FNAs, and 7 (21%) were scrape smears. Most cases (29, 85%) represented primary tumors, 4 (12%) were metastatic deposits, and 1 (3.5%) was a locally recurrent neoplasm. Sites included: pleura/lung 9 (26%), head/neck 8 (24%), lower extremity 7 (21%), trunk 4 (12%), intra-abdominal 3 (9%), upper extremity 2 (7%), and mediastinum 1 (4%). Mean tumor size was 7.2 cm (range: 1.5-19 cm). Three (9%) cases were diagnosed specifically as SFT. Remaining diagnoses were spindle cell neoplasm/proliferation 14 (41%), nondiagnostic 5 (15%), specific type of sarcoma 3 (9%), malignant round cell tumor 2 (6%), sarcoma 2 (6%), malignant tumor 2 (6%) and single cases of melanoma, pleomorphic adenoma, and mesenchymal tumor. Immunohistochemical (IHC) testing was performed in 7 of 27 (26%) cell blocks.

CONCLUSION

SFT FNA cytopathology is morphologically ambiguous, overlapping with a broad array of other spindle cell proliferations. A specific diagnosis is only possible with added staining of STAT6 coupled with a set of other IHC markers.

Extrapleural solitary fibrous tumor of the thyroid gland: A case report and review of literature

BACKGROUND

Solitary fibrous tumor (SFT) is an uncommon mesenchymal neoplasm that arises from the pleura. A few SFTs have also been described in extrapleural sites. However, SFT of the thyroid gland is rare. Here, we report a case of extrapleural SFT on the thyroid gland, in addition to a literature review.

CASE SUMMARY

A 59-year-old man visited our hospital in July 2017 complaining of a large mass in his neck. His thyroid function test results, including antibody levels, were within the normal limits. Ultrasonography showed a 4.7 cm × 4.0 cm × 3.2 cm solitary mass of intermediate suspicion in the left thyroid lobe. A fine-needle aspiration biopsy was subsequently performed. The pathologist reported a benign follicular lesion. However, the size of this nodule increased to 5.5 cm × 5.0 cm × 3.4 cm by April 2018. After a multidisciplinary discussion, a left lobectomy was performed in May 2018. The specimen showed a well-demarcated, partly encapsulated, soft nodule of whitish and tan/brown color on the cut surface. Light microscopy revealed high cellularity with moderate cytologic atypia. The mitotic count was 5/10 high-power fields. There was no tumor necrosis or lymphovascular invasion. The tumor was CD34-positive and signal transducer and activator of transcription 6-positive. Neither thyroid transcription factor-1 nor cytokeratin expression was detected. The Ki-67 showed intermediate proliferative activity. The final diagnosis was extrapleural SFT of the thyroid gland with a clear resection margin. The patient was discharged without complication three days after the surgery.

CONCLUSION

In the literature, extrapleural SFT of the thyroid gland has been reported to behave indolently with the capacity for recurrence and rare metastasis, although surgical resection is the treatment of choice. Understanding this disease entity is important for accurate diagnosis and proper management.

Thyroid Gland Solitary Fibrous Tumor: Report of 3 Cases and a Comprehensive Review of the Literature

Solitary fibrous tumors of the thyroid gland are exceptionally rare. In order to further characterize the clinical and pathologic features of solitary fibrous tumor arising at this anatomic site, three cases of thyroid gland solitary fibrous tumor were analyzed in conjunction with 35 cases compiled from the English literature. Thyroid gland solitary fibrous tumors showed an equal sex distribution with a mean age at presentation of 54.4 years (range, 28-88 years). The patients typically presented with an asymptomatic, slow growing neck mass. Microscopically, the tumors were characterized by cytologically bland spindle cells with patternless growth, hypocellular and hypercellular areas, variable amounts of collagen, and ectatic, branching blood vessels. Two previous reported tumors were considered to be histologically malignant on the basis of increased mitotic activity, profound pleomorphism and tumor necrosis. Immunohistochemically, the tumor cells are variably positive with CD34, bcl-2, and CD99. STAT6 immunohistochemistry, performed on the current cases, demonstrated a strong, diffuse nuclear expression in all tumors. Among 26 patients with available follow up data (mean 47.3 months), one developed local recurrence and distant metastasis. Solitary fibrous tumors occurring in the thyroid gland are uncommon, but can be reliably diagnosed based on the presence of characteristic morphologic features as well as immunohistochemical expression of STAT6 and CD34. The majority of thyroid gland solitary fibrous tumors have exhibited an indolent clinical course, however experience is limited. The rare potential for aggressive clinical behavior requires clinical surveillance.

Malignant solitary fibrous tumor of the thyroid: a case-report and review of the literature

Solitary fibrous tumor (SFT) is an uncommon spindle-cell neoplasm that most often involves the pleura, rarely occurring in extra-thoracic locations. Twenty-six cases of SFT arising in the thyroid gland have been described. We report a case of a 60-year-old woman presenting an 8-month history of enlargement of the neck associated with dysphagia. The patient underwent a right hemithyroidectomy and SFT of the thyroid was diagnosed. Immunohistochemistry showed positivity for CD34 marker, and the high number of mitoses and the presence of cellular atypia suggested that the tumor was malignant. To our knowledge, this is the second case of malignant SFT of the thyroid gland ever reported. Due to the rarity of these tumors, the indication of adjuvant therapy and prognosis are uncertain. Long-term follow-up after surgical resection seems to be advisable.

Solitary fibrous tumor of neck mimicking cold thyroid nodule in 99m tc thyroid scintigraphy

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 of the thyroid gland

Solitary fibrous tumor is a spindle cell neoplasm rarely arising in the thyroid gland. We present a 78-year-old man with the diagnosis of solitary fibrous tumor of the thyroid gland resected by subtotal thyroidectomy. Fine needle aspiration cytology via ultrasound guidance demonstrated a hypocellular aspirate that revealed follicular epithelial cells with mild nuclear atypia and scattered spindle cells with bland nuclei. Histologically, the patternless proliferation of spindle cells was seen among collagenous bundles, accompanied by hemangiopericytomatous vessels, and variously dilated follicles with mild atypical cells having slightly enlarged nuclei, indicating adenomatous goiter. The neoplastic spindle cells showed diffuse immunoreactivity to CD34, bcl-2, CD99 and vimentin, but were negative for cytokeratins, calcitonin, TTF-1 and CD5. Although solitary fibrous tumor arising in thyroid gland is rare, this tumor should be included in the differential diagnosis of thyroid spindle cell tumors and also that of adenomatous.

Intrathoracic thyroid solitary fibrous tumor presenting with respiratory failure

Solitary fibrous tumor (SFT) is an uncommon mesenchymal neoplasm that arises primarily from the pleura, but recognized also in other tissues. SFT in the thyroid gland is extremely rare. Here we presented the second reported SFT arising in an intrathoracic goiter. The88-year-old woman was referred with a huge goiter involving upper mediastinum accompanied by airway obstruction and tracheostomy. The patient underwent a left subtotal thyroidectomy, which revealed a SFT. No recurrence was noted during 3 years of follow-up.

Primary solitary fibrous tumor of the thyroid - report of a case and review of the literature

Solitary fibrous tumor (SFT) is a rare spindle-cell neoplasm, especially in the thyroid. We report a case of primary solitary fibrous tumor of the thyroid gland in a 37 year-old Chinese man. The tumor was characterized by bland-looking spindle cells admixed with thin and thick collagen fibers. On immunohistochemistry study indicated that tumor cells were diffusely positive for CD34, Bcl-2 and CD99, and negative for Desmin, NSE, SMA, S-100, and CD68. The patient remains well 16 months after excision. The morphologic and immunohistochemical features of the thyroid SFTs are similar to their reported counterparts in other anatomic sites.

Solitary fibrous tumor of the liver: a case report

Hepatic solitary fibrous tumor (SFT) is a rare tumor originating from the mesenchyme. Here we report a new case of SFT in the liver and review the clinical presentation, radiological and operative findings, diagnosis, treatment, and outcome. The patient was a 59-year-old man who presented with progressive fatigue for 3 months and an abdominal mass for 3 days. On laboratory tests, no abnormality was detected except that abdominal ultrasonography revealed a 9.0 × 6.2 cm hypoechogenic mass in the left lobe of the liver. A computed tomographic scan confirmed a hypodense lesion in the left lobe of the liver. The patient underwent left hepatectomy. SFT was diagnosed on the basis of histopathological findings. The patient was free from all symptoms and had no signs of local recurrence after 24 months' follow up.

Malignant solitary fibrous tumor of the thyroid gland: report of a case and review of the literature

Solitary fibrous tumors of the thyroid gland (T-SFT) are rarely described, with only 21 cases being reported in the English literatures, all showing benign clinical characteristics. We herein present a 76-year-old woman presenting with a 3-month history of rapidly enlarging neck masses and the CT showed masses with partial calcification in the right thyroid lobe. We performed right hemithyroidectomy and isthmectomy with negative margin under general anesthesia. Histologically, the masses consisted of pleomorphic spindle cells with high mitoses and collagen bands. Immunohistochemically, the tumor cells showed positive reactions for CD34, vimentin and bcl-2, then a diagnosis of malignant solitary fibrous tumor of the right thyroid was made. Six months postoperatively, the CT showed the recurrence of the thyroid tumor and the presence of many nodules of varying sizes throughout bilateral pulmonary lobes. To our knowledge, this is the first case of malignant solitary fibrous tumor of the thyroid gland (T-SFT) with local recurrence and pulmonary metastasis and T-SFT must be considered in the differential diagnosis of spindle cells lesions in the thyroid gland. Correct diagnosis of the malignant T-SFT plays an important role in choosing appropriate therapeutic strategies and long-term follow-up is also extremely essential for these patients.

Solitary fibrous tumor of the adrenal gland with unusual immunophenotype: a potential diagnostic problem and a brief review of endocrine organ solitary fibrous tumor

Solitary fibrous tumor was initially thought to be a pleura-based tumor. However, over the last two decades, its involvement in a variety of extrapleural sites gained recognition. Nonetheless, a primary involvement of the endocrine organs is rare, and in this report, we detail an instance where the tumor affected the adrenal gland of a 71-year-old Arab man. On histology, besides the typical morphologic features seen in solitary fibrous tumor, the neoplasm also exhibited unusual features on immunohistochemistry such as positive staining for cytokeratin AE1/3 and calponin in conjunction with diffuse expression for S-100. The genetic tests for t(X:18) as seen in synovial sarcoma were negative, and the overall histological appearance favored a diagnosis of solitary fibrous tumor. To the best of our knowledge, this report represents the fifth case of a solitary fibrous tumor primarily occurring in the adrenal gland. The differential diagnoses of this neoplasm in our case and a brief summary of solitary fibrous tumor primarily involving the various endocrine organs are presented.