Clinicopathological and genetic heterogeneity of the head and neck solitary fibrous tumours: a comparative histological, immunohistochemical and molecular study of 36 cases

Solitary Fibrous Tumor of Head and Neck Region: A Series of Three Cases at an Uncommon Location With a Review of the Literature

Solitary fibrous tumors (SFTs) uncommonly involve the head and neck region. Head and neck SFTs (HNSFTs) exhibit diverse histological features and can mimic several neoplasms with different treatment and behavior. Herein, we report the clinicopathological features of three cases of HNSFT. Case 1 was a 29-year-old female who presented with a nasal cavity mass measuring 3.5 cm. The patient underwent surgical excision. Microscopic examination revealed classic histological and immunohistochemical (IHC) features of SFT. Unusual histological features included epithelioid morphology, clear cells, and edematous change. She developed local recurrence after 11 months, which was also treated with surgery. Case 2 was a 55-year-old male who developed a 1-cm mass at the buccal mucosa. Surgical excision of the tumor was performed. The tumor was completely circumscribed microscopically. Characteristic histological and IHC features of SFT were identified. Unusual histological features observed were an adenomatous pattern, clear cells, and myxoid change. The patient was alive and disease-free at the 12-month follow-up. Case 3 was a 59-year-old female presenting with a medial canthus mass measuring 1.4 cm. The patient underwent surgical excision. Histological and IHC features observed were diagnostic for SFT. Unusual histological features identified were wavy nuclei and multinucleated stromal giant cells. The patient was alive and disease-free at the 124-month follow-up. Diagnosis of SFT can be challenging in unusual locations like the head and neck region. In addition, the histological spectrum of HNSFT is diverse. Therefore, knowledge about unusual histological features and classic IHC expression is essential for establishing correct diagnosis. Long-term follow-up is recommended because of the risk of recurrence in HNSFT.

Giant cell-rich solitary fibrous tumour of the urinary bladder: case report of an unusual histological variant and literature review

BACKGROUND

Giant cell-rich solitary fibrous tumour (GCR-SFT), previously referred to as giant cell angiofibroma, is an uncommon soft tissue tumour that classically occurs in the orbit but very rarely presents in deep organs. Here, we present a case of GCR-SFT occurring in the urinary bladder, which is one of the unusual histological subtypes of SFT.

CASE PRESENTATION

A 56-year-old man was incidentally found to have a mass measuring 4.5 × 4.3 × 4.0 cm located in the left posterior wall of the bladder by computed tomography during a physical examination. The lesion was confirmed as GCR-SFT by pathological examination after laparoscopic radical surgery. Histopathologically, the tumour was a well-circumscribed, nonencapsulated lesion that was composed of bland spindle-ovoid tumour cells alternating with hypocellular and hypercellular areas, staghorn-like vasculatures and scattered large dark-stained multinucleate giant cells lining pseudovascular spaces. The spindle-ovoid cells and multinucleate giant cells showed strong and diffuse expression of CD34 and nuclear STAT6. In addition, the hallmark of the NAB2ex4-STAT6ex5 fusion gene was detected by RT‒PCR. The patient was classified as having a low risk of recurrence or metastasis according to the risk stratification criteria. The patient underwent regular follow-up for 34 months after surgery, and there was no evidence of local recurrence or metastasis.

CONCLUSION

This is the first reported case of GCR-SFT occurring in the urinary bladder with underlying NAB2ex4-STAT6ex5 fusion. Complete surgical excision of the tumour and long-term follow-up are recommended to ensure no local recurrence or metastasis.

Malignant recurrent orbital solitary fibrous tumor

Solitary fibrous tumor (SFT) is a rare mesenchymal tumor of fibroblastic origin commonly occurring in pleura. It can occur at many extrapleural sites but is rare in orbit. Most cases are benign and recurrence is not unusual in the head and neck and orbit and is usually due to incomplete surgical excision. However, malignant transformation (MT) in orbital SFT is extremely unusual. We present a case of orbital SFT in adult male who developed recurrence with MT eight years after initial surgical excision. He underwent left orbital exenteration. The recurrent tumor revealed features of malignancy with areas exhibiting morphology typical of SFT. The immunochemistry confirmed the diagnosis of SFT with MT. The patient was given adjuvant radiation and was disease free for the last 18 months. Identification of malignancy in orbital SFT is important for the patient to receive appropriate postoperative treatment, as seen in the present case.

A multicentric case study of fibroblastic and myofibroblastic oral spindle cell lesions

Context

Spindle cell lesions comprise a vast plethora of benign and malignant lesions with similar clinical and radiographic features. Their overlapping histopathologic features ensure a diagnostic dilemma.

Aim

The current multicentric study aims to delineate fibroblastic and myofibroblastic oral spindle cell lesions based on cytomorphology and comprehensive immunohistochemical analysis.

Settings and Design

The experimental study was conducted at MS Ramaiah University of Applied Sciences, Bangalore, and All India Institute of Applied Sciences, Delhi.

Methods and Material

A comprehensive histological scoring criteria and panel of immunohistochemical makers (STAT6, CD31, CD34, S100, SMA, vimentin, pan-CK, HHF-35, Ki67, ALK, desmin, HMB-45, SATB2, ERG, EMA and CD99) were employed concurrently for the first time for fibroblastic and myofibroblastic oral spindle cell lesions. The data obtained was tabulated and studied.

Statistical Analysis Used

NA. Results: Using cytological scoring criteria and panel of immunohistochemical makers, the cases analysed and characterized were desmoplastic fibroma, fibrosarcoma, leiomyosarcoma, nodular fasciitis, neurofibroma and epithelioid inflammatory myofibroblastic sarcoma (EIMS).

Conclusions

The diagnostic strategies need to be upgraded for the diagnosis of spindle cell lesions. Emphasis must be placed on cytomorphology, an immunohistochemistry (IHC) panel of markers is imperative for the accurate diagnosis of fibroblastic and myofibroblastic oral spindle cell lesions.

Oral solitary fibrous tumors: A collaborative clinicopathologic study of 19 cases

OBJECTIVE

To report the clinicopathologic features of 19 oral solitary fibrous tumors (SFTs).

METHODS

Clinical data were collected from the records of seven pathology services. All cases were re-evaluated by HE staining and confirmed by immunohistochemistry.

RESULTS

The series comprised 11 females (57.9%) and 8 males (42.1%), with a mean age of 47.3 ± 14.7 years (range: 22-71 years) and a 1.3:1 female-to-male ratio. Most tumors affected the buccal mucosa (n = 7; 36.8%) and presented clinically as an asymptomatic solitary submucosal well-circumscribed nodule with coloration similar to the oral mucosa. Morphologically, most SFTs (n = 10; 52.6%) exhibited a classic hybrid pattern characterized by a well-circumscribed proliferation of densely cellular areas alternating with hypocellular areas in a variably collagenous vascular stroma. Remnants of accessory salivary glands were observed in two cases (n = 2; 10.5%). All tumors were positive for STAT6 and CD34 (n = 19; 100%). Outcome information was available from 6 patients (31.6%), with clinical follow-up ranging from 6 to 24 months (mean ± SD, 9.5 ± 6.8 months), and none developed local recurrence.

CONCLUSIONS

Oral SFTs are rare and often clinically misdiagnosed. Pathologists should consider SFT in the differential diagnosis of oral spindle cell tumors. Accurate diagnosis requires careful morphological evaluation supported by immunohistochemical analysis.

Solitary fibrous tumor of head and neck region; A clinicopathological study of 67 cases emphasizing the diversity of histological features and utility of various risk stratification models

BACKGROUND

Head and neck SFT (HNSFT) exhibit diverse histological features and can mimic various neoplasms with different treatment and behavior. While risk stratification systems have been developed for this tumor at various anatomic sites, a specific scheme for head and neck tumors is lacking. Our aim was to describe the histologic patterns present in HNSFT cases as well as assess the utility of risk assessment models in this location.

METHODS

A retrospective review of pathology reports and microscopy glass slides of HNSFT cases diagnosed between January 2010 and August 2022 was performed.STAT6 was additionally performed on selected cases if needed. Follow up was obtained and various risk stratification models were applied.

RESULTS

Sixty seven cases of HNSFT were collected (age range from 11 to 87 years; median 42 years; M:F 1.6:1). Most common tumor sites were orbit (n = 21; 31.3 %), sinonasal tract (n = 18; 26.9 %), and oral cavity (n = 13; 19.4 %). Tumor size ranged from 1 to 16 cm (median 4cm). Apart from common histological features, tumor cells also showed focal epithelioid morphology, clear cell change and nuclear atypia in a subset of cases. Stromal findings included myxoid and lipomatous change, pseudoglandular spaces, pseudovascular spaces and multinucleated stromal giant cells. CD34 and STAT6 were expressed in 57/67 (85.1 %) and 56/56 (100 %) cases, respectively. Recurrence was observed in 4/26 (15.4 %) cases, while none (0/22) of the patients experienced distant metastasis (follow up 1-150 months; median 20.5 months). Clinical outcome was partially concordant with risk-categories of different risk stratification models.

CONCLUSION

Knowledge about histological diversity of HNSFT is essential for establishing correct diagnosis. Current risk stratification models do not perfectly predict outcome, and larger studies are needed to develop more accurate criteria for aggressive behavior.

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

RATIONALE

A solitary fibrous tumor (SFT) is an uncommon soft tissue tumor that was first discovered in the pleura. Although SFTs have been documented in other extra-pleural sites, an SFT in the thyroid gland is highly unusual. An SFT of the thyroid gland can be difficult to diagnose, and there is little information about their Underlying biological behavior.

PATIENT CONCERNS

We present a case of a 63-year-old man with a progressively growing left-neck mass detected 1 month ago, which was pathologically confirmed to be a benign SFT of the thyroid gland.

DIAGNOSIS

Postoperative pathological examination of the tumor revealed an SFT. Immunopathological examination was consistent with the diagnosis of an SFT.

INTERVENTIONS

The patient underwent surgical resection of the SFT.

OUTCOMES

The patient was recurrence-free during 1.5 years of follow-up.

LESSONS

Surgical excision is beneficial in SFTs that show no histological signs of malignancy, such as pleomorphism, enhanced mitotic activity, necrosis, bleeding, or capsular invasion. However, because the biologic activity remains unknown, meticulous long-term monitoring is required.

A Low Grade Nasopharyngeal sarcoma With FUS::NACC1 Fusion and Immunohistochemical Evidence of Epithelial Differentiation: Expanding the Clinicopathologic Spectrum of an Emerging Entity

BACKGROUND

RNA sequencing of unclassified soft tissue tumors has allowed for definition of multiple new entities. Antonescu et al. recently reported three case of low grade sarcoma with recurrent EWSR1/FUS::NACC1 fusion and distinctive storiform architecture that were suggestive of a novel tumor type.

METHODS

Here, we present a case of an additional sarcoma with FUS::NACC1 fusion that arose in the head and neck and showed immunohistochemical evidence of epithelial differentiation.

RESULTS

A 41 year old woman presented with throat and inner ear pain and was found to have a nasopharyngeal mass. Biopsy highlighted a spindle cell neoplasm composed of bland cells arranged in a tight storiform pattern. On immunohistochemistry, the tumor cells were focally positive for S100 in a fibrillary pattern but were also positive for high molecular weight cytokeratin, p40, and CD34. RNA sequencing demonstrated a FUS::NACC1 fusion. The patient remains free of disease 2 years after surgical resection.

CONCLUSION

These findings confirm the previously-reported recurrent storiform histology in sarcomas with EWSR1/FUS::NACC1 fusion while simultaneously expanding the immunohistochemical spectrum of this entity to include overt epithelial differentiation. With involvement of a head and neck mucosal site, these findings also expand the differential diagnosis to include multiple mesenchymal entities including spindle cell squamous cell carcinoma. Further recognition of this emerging entity via expanded RNA sequencing panels will be necessary to determine the prevalence of these unique features.

Orbital solitary fibrous tumours: clinicopathological characteristics and recurrence prediction

BACKGROUND

SFTs are thought to have an unpredictable clinical course and currently have no recognized prognostic criterion. Our study aimed to determine the relationship between clinicopathological characteristics and the prognosis of patients with orbital SFTs.

METHODS

The clinicopathological features of these patients were extracted from clinical records. The relationships between these features and prognosis were analysed.

RESULTS

The positive rates of CD34, CD99, Blc2, and STAT6 expression were 90.3%, 90.3%, 83.9%, and 100%, respectively. The tumour recurrence rate was 38.7%. A higher recurrence rate was observed in patients with Ki67 index ≥ 5 (56.25% vs. 20%, P = 0.038).

CONCLUSION

A Ki67 index ≥ 5 was an effective parameter for predicting tumour recurrence of orbital SFTs. Close follow-up is needed for these patients.

Molecular testing of soft tissue tumors

BACKGROUND

The diagnosis of soft tissue tumors is challenging, especially when the evaluable material procured is limited. As a result, diagnostic ancillary testing is frequently needed. Moreover, there is a trend in soft tissue pathology toward increasing use of molecular results for tumor classification and prognostication. Hence, diagnosing newer tumor entities such as CIC-rearranged sarcoma explicitly requires molecular testing. Molecular testing can be accomplished by in situ hybridization, polymerase chain reaction, as well as next generation sequencing, and more recently such testing can even be accomplished leveraging an immunohistochemical proxy.

CONCLUSION

This review evaluates the role of different molecular tests in characterizing soft tissue tumors belonging to various cytomorphologic categories that have been sampled by small biopsy and cytologic techniques.

A Large Solitary Fibrous Tumor of the Nasal Cavity and Paranasal Sinuses Involving the Anterior Frontal Fossa: A Case Report and Review of the Literature

The Solitary Fibrous Tumor (SFT) is a rare mesenchymal neoplasm that arises mainly from the pleura. The sinonasal tract is generally not affected by SFT, and less than 100 cases have been reported in the English literature to date. We report an extremely rare SFT of the nasal cavity and paranasal sinuses extending into the anterior frontal fossa through the floor of the anterior skull base. To our knowledge, this case is the fourth SFT of the sinonasal tract involving the anterior frontal fossa in the world. Meanwhile, the tumor, measuring 13 × 6 cm in images, is the largest SFT of the sinonasal tract compared to previously reported cases. Three surgical procedures, including a transcranial one, were performed for the patient to achieve complete removal of the tumor. The diagnosis of SFT was established primarily by immunohistochemical positivity for CD34, STAT6, and negativity for S-100 protein. We emphasize the possibility of recurrence in SFT, and close follow-up is necessary with the help of nasal endoscopy and imaging approaches.

Toward Better Understanding and Management of Solitary Fibrous Tumor

Solitary fibrous tumor (SFT) comprises a histologic spectrum of soft tissue neoplasms that are characterized by the unique NAB2-STAT6 gene fusion. Changes in diagnostic terminology and site-specific classification over the past few decades have resulted in a disjointed literature. Complete surgical excision with preservation of function remains the mainstay of treatment. New risk stratification systems including risk factors such as mitotic rate, age, tumor size, and presence of necrosis, among others, can be used to predict risk of recurrence or metastasis. Long-term follow-up after surgical resection is recommended. The clinical manifestations, diagnosis, management, and prognosis of SFT are reviewed here.

A Rare Case of a Solitary Fibrous Tumor in a Child, Presenting as a Congenital Mass, Displaying NAB2ex4::STAT6ex2 Gene Fusion with an Incidental Ganglioneuroblastoma

A solitary fibrous tumor (SFT) is a ubiquitous tumor that occurs across all ages. It is rarely reported in pediatric patients, especially as a congenital mass. A 1 year 7-month old male child presented with a slow-growing gluteal mass since birth along with a recent episode of bleeding. Magnetic resonance imaging (MRI) showed a well-defined, T1-hypointense and T2-hyperintense mass in the skin and the subcutaneous plane. Subsequently, he underwent a surgical resection that revealed a 5.7 cm-sized fleshy mass. On histopathologic examination, there was a fairly well-circumscribed, cellular spindle cell tumor, with cells arranged in intersecting fascicles and hemangiopericytomatous pattern with areas of hemorrhage and fibrinoid necrosis. Cells revealed mild nuclear atypia. Mitotic figures were up to 8/10 hpf. Immunohistochemically, the tumor cells were diffusely positive for CD34 and STAT6. Furthermore, the tumor revealed NAB2 exon 4:: STAT6 exon 2 fusion by RT-PCR and Sanger sequencing. Post-excision, during follow-up, the patient developed an adrenal mass that was histopathologically proven as a neuroblastic tumor, not further specified on biopsy and finally as ganglioneuroblastoma, intermixed type on excision. This constitutes one of the rare cases of SFT in a pediatric patient, presenting as a congenital mass, confirmed by STAT6 immunostaining and further, molecular testing. A review of literature of similar cases, including treatment-related implications, is presented.

Giant cell-rich solitary fibrous tumour of the lacrimal gland with prominent angiomatoid cystic changes and an underlying NAB2ex3-STAT6ex18 fusion

Giant cell-rich solitary fibrous tumour (GCR-SFT) is a rare variant of SFT with a predilection for the orbital region. Despite its hypervascularity, extensive angiomatoid cystic changes are unusual in GCR-SFT and may pose a diagnostic challenge. A 47-year-old man presented with a right eye proptosis and a protruding tumour of several years’ duration with recently accelerated tumour growth. MRI revealed a cystic-solid heterogeneous mass arising from the lacrimal gland and displacing the globe. A subtotal excision of the mass was performed due to unanticipated hypervascularity and intraoperative bleeding. Pathologically, a vascular neoplasm was initially suspected. The diagnosis of GCR-SFT was made following careful evaluation and demonstration of CD34 and STAT6 expression. Molecular studies revealed a pathognomonic but rare NAB2ex3-STAT6ex18 fusion variant as well as a TP53 mutation suggestive of aggressive phenotype. The patient had a complete resolution of the proptosis but the clinical picture remains guarded due to incomplete resection.

Primary solitary fibrous tumor of the thyroid gland: A review starting from a case report

Primary solitary fibrous tumor (SFT) of the thyroid gland is a rare mesenchymal tumor with fibroblastic differentiation, ramified, thin-walled, enlarged (staghorn) vessels and specific NAB2-STAT6 gene fusion, which is more commonly found in pleura and peritoneum. This neoplasm can be located in a variety of anatomical sites outside pleura and peritoneum including bone, visceral organs and soft tissues, head and neck examples representing only 10-15% of the extra-pleural and extra-peritoneal tumors. Diagnosing this entity can be difficult, especially in thyroid gland, mainly because of the rarity of this neoplasm, but presence of characteristic microscopic features together with positivity for STAT6 and CD34 can confirm the diagnosis and exclude other differential diagnosis. Information about the diagnosis and treatment options of thyroid SFTs is limited but almost all primary thyroid SFTs have a good prognosis and indolent clinical course. Clinical surveillance is still necessary because some SFTs can be aggressive. Raising awareness regarding extra-pleural and extra-peritoneal location of this tumor in endocrine organs can help to better manage these patients. We report the case of a 34-year-old female with primary SFT of the thyroid gland. Additionally, we review the literature for the main clinical, paraclinical and pathological features of this neoplasm.

A Case Report of a Solitary Fibrous Tumor of the Maxillary Sinus

A solitary fibrous tumor (SFT) is a benign neoplasm, firstly described as a mesenchymal tumor of the pleura. Its incidence range in the head and neck region is about 5–27%, but only rarely does it affect paranasal sinuses. The differential diagnosis is challenging, owing to its erosive growth pattern and immuno-histochemical features. SFTs have an aggressive behavior and an important recurrence potential. Therefore, a radical surgical excision is the gold standard therapeutic procedure. A rare SFT originating from the right maxillary sinus is reported here. The 37-year-old patient presented to the outpatient clinic with a painful expansive lesion in the whole right maxillary region. The overlying skin was inflamed and the patient had no epistaxis episodes. The 1.5 dentary element tested negative for vitality; however, a puncture of the lesion led to a hematic spill and no purulent discharge. An endoscopic-guided biopsy was suggestive either of SFT or hemangioperictoma, excluding a malignant neoplasm. A multi-equipe surgical team was activated. The lesion was embolized in order to achieve a good hemostatic control and, after 48 h, the neoplasm was radically excised with a combined open and endoscopic approach. The patient was disease-free at 12-month radiological and clinical follow-up. Given the rarity of this lesion and the delicacy required in addressing head and neck neoplasms, we believe that the present case report might be of help in further understanding how to approach cranio-facial SFTs.

STAT6: A review of a signaling pathway implicated in various diseases with a special emphasis in its usefulness in pathology

Signal Transducer and Activator of Transcription 6 (STAT6), belonging to a family of seven similar members is primarily stimulated by interleukin(IL)-4 and IL-13, and acts as a T helper type 2 (Th2)-inducing factor. Thus, it is implicated in the pathophysiology of various allergic conditions, such as asthma, atopic dermatitis, eosinophilic esophagitis and food allergies, but also in tumor microenvironment regulation. Furthermore, certain forms of lymphomas, notably the Hodgkin lymphoma group, the primary mediastinal and primary central nervous system lymphoma, as well as some follicular and T cell lymphomas are associated with dysregulation of the STAT6 pathway. STAT6 immunohistochemical expression also serves as a surrogate marker in the diagnosis of solitary fibrous tumor, despite not directly responsible for the tumorigenic effect. These pathophysiological implications of the STAT6 pathway, its diagnostic or prognostic role in pathology, as well its immunohistochemical detection with different antibodies will be discussed in this review.

Lipomatous Solitary Fibrous Tumors Harbor Rare NAB2-STAT6 Fusion Variants and Show Up-Regulation of the Gene PPARG, Encoding for a Regulator of Adipocyte Differentiation

Solitary fibrous tumors (SFTs) harbor activating NAB2-STAT6 gene fusions. Different variants of the NAB2-STAT6 gene fusion have been associated with distinct clinicopathologic features. Lipomatous SFTs are a morphologic variant of SFTs, characterized by a fat-forming tumor component. Our aim was to evaluate NAB2-STAT6 fusion variants and to further study the molecular genetic features in a cohort of lipomatous SFTs. A hybrid-capture-based next-generation sequencing panel was employed to detect NAB2-STAT6 gene fusions at the RNA level. In addition, the RNA expression levels of 507 genes were evaluated using this panel, and were compared with a control cohort of nonlipomatous SFTs. Notably, 5 of 11 (45%) of lipomatous SFTs in the current series harbored the uncommon NAB2 exon 4-STAT6 exon 4 gene fusion variant, which is observed in only 0.9% to 1.4% of nonlipomatous SFTs. Furthermore, lipomatous SFTs displayed significant differences in gene expression compared with their nonlipomatous counterparts, including up-regulation of the gene peroxisome proliferator activated receptor-γ (PPARG). Peroxisome proliferator activated receptor-γ is a nuclear receptor regulating adipocyte differentiation, providing a possible explanation for the fat-forming component in lipomatous SFTs. In summary, the current study provides a possible molecular genetic basis for the distinct morphologic features of lipomatous SFTs.

Giant Cell Angiofibroma in Sublingual Area: A Case Report and Review of Literature

We present a case of Giant Cell-Rich Solitary Fibrous Tumor also known as Giant cell angiofibroma, occuring in sublingual region, to our knowledge, which has never been reported before. Forty-nine years old female who presented with painless, slowly growing mass in the sublingual region underwent excisional surgery and was diagnosed with giant cell-rich solitary fibrous tumor previously referred to as giant cell angiofibroma. In our report, we aimed to report the unusual localization of this rare tumor, examine the new nomenclature and classification of giant cell-rich solitary sibrous tumor or giant cell angiofibroma and review the literature regarding head and neck localization of this tumor.

Oral Solitary Fibrous Tumor: A Retrospective Clinico-Pathological Study and Long-Term Follow-Up

Background and Objectives: This was a retrospective single-center study to analyze and describe the clinical and histological features of all cases of oral solitary fibrous tumor (SFT). Study design: the study included all consecutive cases of oral SFT diagnosed between 2008-2018 at a single tertiary center. Materials and Methods: Clinical data was retrieved from medical charts. The diagnosis of oral SFT was based upon the morphologic features of the lesions, in routine hematoxylin and eosin (H&E) stained sections and confirmed by immunohistochemical analyses including CD34, CD99, Bcl2, and stains for STAT6. Results: Seven cases of oral SFT were found. Of these, three (42%) were in males and four (58%) in females. The age range was 24-63 years (mean 47 ± 13). Four (58%) lesions were located in the buccal mucosa, two (28%) in the labial mucosa and one (14%) on the floor of the mouth. The diameter ranged between 3-50 mm (mean 22 ± 14 mm). All patients were treated with local excision. Follow-up periods were between 2-74 months (mean 41 ± 27). No recurrences were reported. Conclusions: We present a series of oral SFT, which were all non-aggressive in presentation and did not recur after conservative surgery (local excision) over a relatively long follow-up period.

Endoscopic resection of solitary fibrous tumor of the ethmoid: Case report review of the literature

INTRODUCTION

Solitary fibrous tumour (SFT), as are benign neoplasms of fibroblastic cells. Nasosinusal localisation is exremely rare, difficult to diagnose and to manage.

CASE REPORT

We report a rare case of Solitary fibrous tumour in the nasal cavity in a 47-year-old- woman, with complete surgical resection.

DISCUSSION

SFTs are of mesenchymal origin, mainly from serous membranes. The head and neck region is affected with a percentage ranging from 5 to 27%. On the other hand, LTS unusually affects the nasal tract (NTS). Because of this rarity and its variable morphological appearance, it is difficult to distinguish TNS from other mesenchymal lesions.

CONCLUSION

Although there are no standard clinical guidelines, the preferred treatment for FLS is radical surgical resection.

Orbit Solitary Fibrous Tumor: A Proposed Risk Prediction Model Based on a Case Series and Comprehensive Literature Review

Solitary fibrous tumors (SFTs) of the orbit are rare. In order to further characterize the clinical and pathologic features of solitary fibrous tumor arising at this anatomic site, 12 cases of orbital SFTs were analyzed in conjunction with a review of 263 cases reported from the English literature in order to develop a risk prediction model. SFTs of the orbit were equally distributed between males (n = 5) and females (n = 7) with a mean patient age of 46.8 years (median 44.5 years; range 18-76 years) at initial diagnosis. The patients typically presented with swelling or mass around the orbit, with proptosis (n = 10), ptosis (n = 5), and visual changes (n = 6). Tumors were orbital (n = 10) or upper eyelid (n = 2). Mean tumor size was 2.5 cm (median 2.6 cm). 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. By immunohistochemistry, all cases had a strong nuclear STAT6 expression. All patients were initially managed with excision or biopsy, three with presurgical embolization. The two patients with biopsy only had persistent disease (mean 37.2 months), but a third patient developed distant bone metastasis at 86.9 months. Overall mean follow-up was 73.1 months: 9 patients are alive or dead without disease (mean 77.9 months), two patients with persistent disease, and one patient with metastatic disease at last follow-up (102 months). Incorporating cases sufficiently reported in the literature, a risk prediction model based on age > 45 years, tumor size > 3 cm, tumor necrosis, mitoses of > 4/2 mm², moderate to high cellularity, and moderate to severe pleomorphism allows for risk stratification for the development of local recurrence and distant metastasis. In conclusion, orbital SFTs are rare, but can be reliably diagnosed based on the presence of characteristic morphologic features and STAT6 immunohistochemistry. Orbital tumors tend to show a higher frequency of local recurrence than distant metastasis, which can be predicted by a risk stratification model unique to orbital tumors. With late disease common, long term clinical follow-up is recommended.

Clinicopathologic Analysis of Oral and Maxillofacial Solitary Fibrous Tumor

OBJECTIVES

The aim of this systematic review was to provide an overview of the oral and maxillofacial solitary fibrous tumor (SFT) in order to determine its clinicopathologic characteristics and biological behavior.

METHODS

We conducted a systematic review in May 2019 in multiple databases. Cases diagnosed as SFT in the oral cavity and maxillofacial complex were included.

RESULTS

Seventy-three published articles were included in our systematic review, corresponding to a total of 154 cases. SFT showed a slight female predilection (53.2%), and the cheek mucosa/cheek, tongue, and palate were the most affected anatomical sites. The mean size of SFT in the oral cavity and maxillofacial region at diagnosis was 1.4 cm. Histologic features of malignancy by morphologic analysis (P < .001) were significantly associated with a larger tumor size. Surgical excision was the most frequent therapeutic modality. Recurrence and metastasis were uncommon findings in our sample.

CONCLUSIONS

Histologic features of malignancy can be important parameters of tumor behavior. Adequate surgical treatment and long-term follow-up are required for these cases.

Orbital solitary fibrous tumors: a multi-centered histopathological and immunohistochemical analysis with radiological description

BACKGROUND

Solitary fibrous tumors (SFT), formerly called hemangiopericytoma, are rare tumors derived from mesenchymal cells originally described in the pleura, but these tumors may affect extraserosal tissues including the lacrimal gland and orbit.

OBJECTIVE

Conduct a multi-centered clinical, radiological and histopathological analysis of 17 orbital SFT cases.

DESIGN

A retrospective case series.

SETTING

Three eye centers in two countries.

PATIENTS AND METHODS

The data collected from the charts of 17 adult patients presenting with tissue diagnosis of orbital hemangiopericytoma or SFT from January 2003 to December 2018 included demographics, clinical imaging and histopathological information including immunohistochemical (IHC) characteristics.

MAIN OUTCOME MEASURES

The demographic characteristics, clinical presentation, and histopathological patterns or variants of SFT were analyzed.

SAMPLE SIZE

17 adult patients.

RESULTS

Mean age was 45 years (range 23-80 years). Male to female ratio was 3:1. The right eye was affected in 12 (70.5%) patients. Commonest presentation was proptosis in 13/17 (76% of patients). Other symptoms were impaired motility (29%) and ptosis (11%). Lesions mostly affected the medial orbit (35%), then orbital apex in 11%. The histopathological classic pattern-less variant was the commonest. One case with aggressive behavior, multiple recurrences and atypical features was encountered. Immunohistochemical (IHC) markers used included CD34 expression in all cases, Bcl-2 expression in 10/11, CD99 in 9/9 and Vimentin in 4/4. STAT6 was used in 2 cases.

CONCLUSIONS

SFTs are rare tumors affecting the orbit in both genders equally in their mid-forties, but showed male predominance in our analysis with a predominant classic histopathological pattern. Tissue diagnosis is essential and requires IHC studies for confirmation.

LIMITATIONS

Sample size is relatively small owing to the rarity of this tumor in the orbit.

CONFLICT OF INTEREST

None.

Solitary fibrous tumors of the head and neck region revisited: a single-institution study of 20 cases and review of the literature

A solitary fibrous tumor (SFT) is a rare, NAB2-STAT6 fusion gene-associated mesenchymal neoplasm. It most commonly arises in the pleural site, but it can occur at many other sites, and rarely also in the head and neck (H&N) region. STFs may show many growth patterns and therefore can be easily mistaken for other more common H&N spindle cell or epithelial lesions. In this study, we present our experience in the diagnosis of 20 cases of SFT in the H&N region and discuss their most notable mimickers. In all cases, STAT6 expression was found positive by immunohistochemistry, and the NAB2-STAT6 fusion was confirmed by next-generation sequencing. Three major fusion variants were detected: NAB2ex2-STAT6int1 (5/20, 25%), NAB2ex6-STAT6ex16 (4/20, 20%), and NAB2ex4-STAT6ex2 (3/20, 15%). Clinical follow-up was available for 16 patients (median follow-up time: 84 months). One patient with a morphologically malignant SFT experienced multiple local recurrences, followed by dissemination into the lungs and meninges. This malignant SFT also displayed an aberrant FLI1 expression, which was not previously reported in SFT cases. We also summarize findings from 200 cases of SFT of the H&N region, which included cases from our study, and from previous studies that reported on the fusion status of the STAT6 gene. The results suggest that metastatic disease developed only in cases with STAT6 variants that included the DNA-binding domain (STAT6-full variants), which contradicts expectations from previous reports and deserves further investigation.

Soft Tissue Special Issue: Fibroblastic and Myofibroblastic Neoplasms of the Head and Neck

Fibroblastic and myofibroblastic neoplasms of the head and neck encompass a group of rare tumor types with often overlapping clinicopathologic features that range in biologic potential from benign to overtly malignant. Even neoplasms with no metastatic potential may provide significant therapeutic challenges in this region due to the unique anatomy of the head and neck. This review will cover the following entities, highlighting important clinical aspects of each neoplasm and then focusing on their characteristic histomorphology, immunophenotype, and molecular alterations: nodular and cranial fasciitis, fibrous hamartoma of infancy, nasopharyngeal angiofibroma, nuchal-type and Gardner fibromas, desmoid fibromatosis, dermatofibrosarcoma protuberans and giant cell fibroblastoma, solitary fibrous tumor, inflammatory myofibroblastic tumor, low-grade myofibroblastic sarcoma, infantile fibrosarcoma, low-grade fibromyxoid sarcoma, and sclerosing epithelioid fibrosarcoma. While some of these neoplasms characteristically arise in the head and neck, others are rarely described in this anatomic region and may therefore be particularly difficult to recognize. Distinction between these entities, however, is crucial, particularly as the molecular pathogenetic basis for these neoplasms are being rapidly elucidated, in some instances allowing for targeted therapeutic approaches.

Solitary Fibrous Tumors in the Head and Neck: Comprehensive Review and Analysis

Solitary fibrous tumors (SFT) arising in the head and neck region are uncommon yet well-recognized entities. Their biologic behavior and management still need to be elucidated. Systematically reviewing all published cases of SFT involving the head and neck region since 1991, a pooled meta-analysis was conducted to evaluate various demographic and tumor characteristics. 587 SFT in the head and neck have been reported; 343 met pooled analysis inclusion criteria. 61% of cases presented as a new mass; 89% were painless. Median onset of symptoms prior to evaluation was 8 months. Pre-operative local invasion and malignant histological features (hemorrhage, necrosis, mitoses > 4/10 hpf) were not statistically associated with decreased recurrence-free survival. Positive surgical margins was the only factor associated with shorter recurrence-free survival (p < 0.001). The evidence presented herein reveals novel associations between clinical presentation and tumor characteristics that provide otolaryngologists with new insight into SFT tumor behavior, thus prompting further investigations.

Molecular changes in solitary fibrous tumor progression

Abstract

Solitary fibrous tumors (SFTs) are NAB2-STAT6 fusion-associated neoplasms. There are several subtypes of NAB2-STAT6 fusions, but their clinical significances are still unclear. Moreover, the mechanisms of malignant progression are also poorly understood. In this study, using 91 SFT cases, we examined whether fusion variants are associated with clinicopathological parameters and also investigated the molecular mechanism of malignant transformation using whole-exome sequencing. We detected variant 1b (NAB2ex4-STAT6ex2) in 51/91 (56%) cases and variants 2a/2b (NAB2ex6-STAT6ex16/17) in 17/91 (19%) cases. The NAB2-STAT6 fusion variant types were significantly associated with their primary site (P < 0.001). In addition, a TERT promoter mutation was detected in 7/73 (10%) cases, and it showed a significant association with malignant SFTs (P = 0.003). To identify molecular changes during malignant progression, we selected an index patient to obtain parallel tissue samples from the primary and metastatic tumors. In the metastatic tissue, 10 unique molecular alterations, including those in TP53 and APAF1, were detected. In vitro functional experiments showed that APAF1 depletion increased the tumor potency of cells expressing NAB2-STAT6 fusion protein under treatment with staurosporine. We found that TP53 immunopositivity (P = 0.006) and loss of APAF1 immunoreactivity (P < 0.001) were significantly associated with malignant SFTs. Our study suggests that dysfunction of TP53 and APAF1 leads to impaired apoptotic function, and eventually contributes toward malignant SFT transformation.

Key messages

We firstly found that the TERT promoter mutation was strongly associated with malignant SFTs (P = 0.003) and the representative 1b (NAB2ex4-STAT6ex2) or 2a (NAB2ex6-STAT6ex16) fusion variants similarly contribute to tumorigenicity.

We also found that TP53 immunopositivity (P = 0.006) and loss of APAF1 immunoreactivity (P < 0.001) were significantly associated with malignant SFTs.

Our study suggests that dysfunction of TP53 and APAF1 leads to impaired apoptotic function, and eventually contributes toward malignant SFT transformation.

Electronic supplementary material

The online version of this article (10.1007/s00109-019-01815-8) contains supplementary material, which is available to authorized users.

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.

Recurrent Sinonasal CD34-Negative Malignant Solitary Fibrous Tumor Diagnosed on STAT6 Immunohistochemistry and NAB2-STAT6 Fusion

A spectrum of mesenchymal neoplasms occur in the sinonasal region. One of these is solitary fibrous tumor (SFT), a translocation-associated neoplasm characterized by NAB2-STAT6 gene fusion. Sinonasal SFTs characteristically display CD34 immunopositivity, which aids in diagnosis. However, a small proportion of SFTs may be negative for CD34, making diagnosis difficult. The availability of STAT6 immunohistochemistry (IHC) has helped to overcome this. Malignant SFTs, characterized by increased cellularity and mitoses > 4 per ten high power fields, are extremely unusual in the sinonasal region, with only ten such cases reported to date. We report a case of a CD34-negative malignant SFT that was diagnosed using STAT6 IHC and confirmed by demonstrating NAB2 ex 4-STAT6 ex 2 fusion, and recurred 8 months after complete excision, to highlight the aggressive nature of this tumor.

Salvage preoperative embolization of an infratemporal solitary fibrous tumor: A case report with review of the literature

RATIONALE

Head and Neck Solitary fibrous tumors (SFT) are very rare. They could be misdiagnosed as hemangiopericytomas (HPC).

PATIENT CONCERNS

We report a 60 y o lady presenting with sinonasal mass, causing recurrent profuse bleeding.

DIAGNOSES

Hemangioperocytomas versus SFT were among the differentials, according to Radiological studies. Upon Biopsy, the diagnosis of SFT has been adopted.

INTERVENTIONS

Salvage pre-operative embolization resulted in bleeding control, bridging the patient to surgery.

OUTCOMES

Post-operative course was uneventful, and patient symptoms resolved.

LESSONS

This is the first case report of a sinonasal SFT, where pre-operative embolization has been employed as a salvage procedure. This treatment modality is promising, since it controls bleeding, bridges patient to surgery and decreases blood loss during the surgical procedure.

An update on mesenchymal tumours of the orbit with an emphasis on the value of molecular/cytogenetic testing

Mesenchymal tumours of the orbit are uncommon. Beyond childhood primary sarcomas are extremely rare and the literature is limited to case reports and short case series. However there is a diverse assortment of benign and malignant soft tissue tumours that may involve the orbit. Techniques to identify tumour specific cytogenetic or molecular genetic abnormalities often resulting in over- expressed proteins are becoming an increasingly important ancillary technique for these tumours. This review focuses on 3 specific areas: 1. Orbital mesenchymal tumours where cytogenetics are important to reach the correct diagnosis. The majority of these are chromosomal translocations that often result in a fusion gene and protein product; 2. Orbital mesenchymal tumours where cytogenetics are important to identify patients who will do well versus those with a poorer prognosis. This is turn helps with therapeutic options. In some tumours e.g. synovial sarcoma the chromosomal translocations can occur with 2 different regions resulting in different fusion products that carry a different prognosis. Alternatively whilst the majority of alveolar rhadomyosarcomas are fusion positive a minority are fusion negative with a better prognosis; 3. Orbital mesenchymal tumours where the identification of specific cytogenetic abnormalities has resulted in overexpression of specfic proteins which are diagnostically useful biomarkers for immunohistochemistry.

Sinonasal Tract Solitary Fibrous Tumor: A Clinicopathologic Study of Six Cases with a Comprehensive Review of the Literature

Solitary fibrous tumors (SFTs) are well recognized in the head and neck region, but rarely arise in the sinonasal tract (SNT). Six primary SNT SFTs were identified in the files of Southern California Permanente Medical Group between 2006 and 2017. The patients included five males and one female ranging in age from 33 to 72 years (mean 52 years), most of whom presented clinically with nasal obstruction. Three tumors involved the nasal cavity alone, one involved the paranasal sinuses, and two involved both the nasal cavity and paranasal sinuses. Histologically, the tumors were characterized by a variably cellular proliferation of cytologically bland spindle cells within a collagenous stroma with prominent interspersed branching vessels. Mitotic activity was low (range 0-2 per 10 high power fields) and there was no evidence of pleomorphism or tumor necrosis. Surface ulceration was noted. By immunohistochemistry, the lesional cells were positive for CD34, STAT6 and bcl-2. Clinical follow up information was available for all patients (range 32-102 months; mean 72 months). There were no recurrences or metastases and all were alive with no evidence of disease at last follow-up. SFTs rarely affect the SNT, but should be considered in the differential diagnosis of SNT mesenchymal lesions. Immunohistochemical expression of STAT6 can aid in diagnosis and separation of SFT from other spindle cell lesions occurring at this anatomic site. In combination with cases reported in the literature, primary SNT SFT behave in an indolent manner with conservative treatment.

Solitary Fibrous Tumors of the Head and Neck: A Multi-Institutional Clinicopathologic Study

Solitary fibrous tumors (SFTs) of the head and neck are uncommon. Lesions previously diagnosed in the head and neck as hemangiopericytomas (HPCs), giant cell angiofibromas (GCAs), and orbital fibrous histiocytomas (OFHs) are now recognized as within the expanded spectrum of SFTs. To better understand the clinicopathologic profile of head and neck SFTs, we performed a multi-institutional study of 88 examples. There was no sex predilection (F:M ratio 1.2), and the median patient age was 52 years (range: 15 to above 89 y). The sinonasal tract and orbit were the most common sites involved (30% and 25%), followed by the oral cavity and salivary glands (15% and 14%). Original diagnoses included HPC (25%), SFT (67%), and OFH (6%), with 1 SFT and 1 OFH noted as showing GCA-like morphology. On review, the predominant histologic pattern was classic SFT-like in 53% and cellular (former HPC-like) in 47%; lipomatous differentiation (8%) and GCA-like pattern (7%) were less prevalent. Subsets demonstrated nuclear atypia (23%), epithelioid morphology (15%), or coagulative necrosis (6%). Infiltrative growth (49%) and osseous invasion (82%) were prevalent among evaluable cases. Of the 48 SFTs with follow-up (median: 43 mo), 19 showed recurrence (40%). Of these, 4 patients were alive with disease and 4 dead of disease. Size and mitotic rate were negative prognosticators using a joint prognostic proportional hazards regression model. Three patients experienced metastasis, to lungs, parotid, bone, and skull base, including one case showing overtly sarcomatous "dedifferentiation." As a group, SFTs present in a wide anatomic and morphologic spectrum in the head and neck. Only rare examples metastasize or cause death from disease. However, the fairly high local recurrence rate underscores their aggressive potential and highlights the importance of prospective recognition.

Solitary fibrous tumour of the genitourinary tract: a clinicopathological study of 11 cases and their association with the NAB2-STAT6 fusion gene

AIMS

To characterise clinicopathological features and clinical outcomes of the genitourinary tract solitary fibrous tumours, incorporating NAB2-STAT6 gene fusion status.

METHODS

The presence of the molecular hallmark NAB2-STAT6 gene fusion and for the defining fusion partner product STAT6 was assessed in 11 cases of the genitourinary tract solitary fibrous tumours. NAB2-STAT6 gene fusion analysis was performed using a break-apart fluorescence in situ hybridisation (FISH) probe using a probe cocktail with Bacterial artificial chromosome (BAC) clones for STAT6 and NAB2.

RESULTS

Eleven solitary fibrous tumours were diagnosed in eight male patients and three female patients with a mean age of 46 years (range: 11-64 years). Four of the tumours had malignant histological features, and three were considered moderate risk for metastasis. With a mean follow-up time of 61 months, 1 recurred locally and 2 presented at distant metastatic sites. Using a break-apart FISH probe cocktail, we found the NAB2-STAT6 gene fusion and nuclear STAT6 expression in 58% and 91% of cases, respectively. However, the NAB2-STAT6 fusion status was not correlated with STAT6 expression or useful in discriminating between malignant histological features or subsequent clinical outcomes in the genitourinary solitary fibrous tumours.

CONCLUSIONS

A subset of solitary fibrous tumours of the genitourinary tract behaved aggressively. Using a break-apart FISH probe cocktail, we found the NAB2-STAT6 gene fusion in 64% of cases. However, the NAB2-STAT6 fusion status was not correlated with STAT6 expression or useful in discriminating between low-risk or high-risk tumours and subsequent clinical outcomes.

A case of giant cell-rich solitary fibrous tumor in the external auditory canal

We present a rare case of giant cell-rich solitary fibrous tumor (SFT) arising at the left external auditory canal in a 31-year-old woman. The tumor was well-circumscribed and composed of spindle-shaped cells with abundant collagenous bands. Scattered multinucleate giant cells were observed, some of which lined pseudovascular spaces. Although a focal mild-hypercellular area was observed, mitoses were rare and necrosis was absent. Interstitial mast cells were scattered, especially in the hypercellular area. Immunohistochemically, CD34, vimentin, and Bcl-2 presented diffuse positivity. Moreover, both mononuclear spindle cells and multinucleate cells showed nuclear STAT6 positivity, while NAB2-STAT6 fusion gene could not be detected by reverse transcription polymerase chain reaction using formalin-fixed specimen. These findings suggest the pathological diagnosis of giant cell-rich SFT, previously known as giant cell angiofibroma, which is a rare variant of SFT with multinucleate giant cells and occurs predominantly in orbital region. Although giant cell-rich SFTs of extra-orbital sites have been reported, to our knowledge, this is the first case arising in the external auditory canal. Giant cell-rich SFT should be considered as a differential diagnosis of spindle cell lesion with multinucleate giant cells, and STAT6 immunohistochemistry should be performed to distinguish this rare tumor from other mesenchymal neoplasms.