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

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.

MRI-based radiomics nomogram for distinguishing solitary fibrous tumor from schwannoma in the orbit: a two-center study

OBJECTIVES

To investigate the value of magnetic resonance imaging (MRI) radiomics for distinguishing solitary fibrous tumor (SFT) from schwannoma in the orbit.

MATERIALS AND METHODS

A total of 140 patients from two institutions were retrospectively included. All patients from institution 1 were randomized into a training cohort (n = 69) and a validation cohort (n = 35), and patients from institution 2 were used as an external testing cohort (n = 36). One hundred and six features were extracted from T2-weighted imaging (T2WI) and contrast-enhanced T1-weighted imaging (CET1WI). A radiomics model was built for each sequence using least absolute shrinkage and selection operator logistic regression, and radiomics scores were calculated. A combined model was constructed and displayed as a radiomics nomogram. Two radiologists jointly assessed tumor category based on MRI findings. The performances of the radiomics models and visual assessment were compared via area under the curve (AUC).

RESULTS

The performances of the radiomics nomogram combining T2WI and CET1WI radiomics scores were superior to those of the pooled readers in the training (AUC 0.986 vs. 0.807, p < 0.001), validation (AUC 0.989 vs. 0.788, p = 0.009), and the testing (AUC 0.903 vs. 0.792, p = 0.093), although significant difference was not found in the testing cohort. Decision curve analysis demonstrated that the radiomics nomogram had better clinical utility than visual assessment.

CONCLUSION

MRI radiomics nomogram can be used for distinguishing between orbital SFT and schwannoma, which may help tumor management by clinicians.

CLINICAL RELEVANCE STATEMENT

It is of great importance and challenging for distinguishing solitary fibrous tumor from schwannoma in the orbit. In the present study, an MRI-based radiomics nomogram were developed and independently validated, which could help the discrimination of the two entities.

KEY POINTS

• It is challenging to differentiate solitary fibrous tumor from schwannoma in the orbit due to similar clinical and image features. • A radiomics nomogram based on T2-weighted imaging and contrast-enhanced T1-weighted imaging has advantages over radiologists. • Radiomics can provide a non-invasive diagnostic tool for differentiating between the two entities.

Solitary Fibrous Tumours of the Orbit - Clinical Pathology, Therapy and Prognosis

BACKGROUND

Solitary fibrous tumours are rare. The aim of this study is to describe the clinical features, therapy and outcome of affected patients and to identify factors associated with recurrence.

METHODS

Retrospective study of a cohort of 20 patients who underwent surgery for orbital solitary fibrous tumour at the University Department of Oral and Maxillofacial Surgery between 2002 and 2023. Demographic, clinical, and therapeutic data as well as tumour follow-up results were collected. Tumour volume and molecular genetic mutations were retrospectively determined.

RESULTS

The median patient age was 49.5 years at initial surgery. The left orbit was affected in 65% of cases. The most common clinical symptom was proptosis (80%). This was reported with a mean lateral difference of 3.9 mm (range: 1 - 10 mm). The tumours were localised predominantly in the intra- and extraconal space, craniolateral quadrant and middle third. The median tumour volume was 7.66 cm³ (range 2.15 - 12.57 cm³). In all patients, the diagnosis was made by pathological examination. All tumours investigated showed a NAB2-STAT6 mutation. The most frequently detected mutation was the fusion NAB2 exon 4 - STAT6 exon 2. All patients were initially managed with frontolateral orbitotomy. Incomplete resection (R1-status) occurred in 35% (n = 7). The recurrence rate was 25% (n = 5), with a median disease-free interval of 45.5 months (range 23 - 130). 80% (n = 4) of recurrences were initially R1-resected.

CONCLUSION

Orbital solitary fibrous tumours are rare tumours and are clinically manifested by signs of displacement of orbital structures. Diagnosis is made by histology and immunohistochemistry and can be proven with the molecular genetic detection of the NAB2-STAT6 mutation. The therapy of choice is complete surgical resection. R1-resection is more likely in the intraconal location as well as in location in the posterior third of the orbit - due to difficult surgical accessibility. The greatest risk factor for the development of recurrence is incomplete surgical excision. Late recurrences are possible, which is why a long-term connection to a specialised clinic is necessary.

Presentation of orbital solitary fibrous tumours

AIMS

To evaluate presenting features of patients with orbital solitary fibrous tumours (SFTs), based on histological phenotype.

METHODS

A retrospective case-note review was performed for demographics and presenting features for patients with orbital SFTs. The tumours were classified as "Group IA" hypocellular SFT phenotype, "Group IB" haemangiopericytoma phenotype and low mitotic activity, and high-grade "Group II" haemangiopericytoma phenotype with high mitotic activity.

RESULTS

Sixty-four patients (34 female; 53%) presented at a mean age of 42.2 years (median 38; range 19-82), with Group II patients presenting at an older age (mean 53 years). Median symptom duration was 12 months for Groups IA and IB, compared to 4 months for Group II, the commonest symptoms being proptosis (53%), diplopia (41%), periorbital swelling (31%), and altered vision (19%). Mean LogMAR was 0.17 (median 0.0; range -0.2-4), and 14% had ipsilateral optic neuropathy, with no significant difference between the three groups. Non-axial displacement was noted in 69%, a palpable mass in 45%, and reduced eye movements in 59%; choroidal folds and optic disc swelling were recorded in 12% and 9%. SFTs were mostly extraconal (59%), within the superior and superonasal quadrants (44%), with an average estimated tumour volume of 4.9 ml (median 3.6; range 0.31-14.5 ml).

CONCLUSION

SFTs may present with impaired visual function (∼15%), fundal abnormalities (a fifth), globe displacement (two-thirds), and reduced ocular motility (over a half). High-grade tumours tend to present more than a decade later, with a shorter duration of symptoms.

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.

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 review of solitary fibrous tumours of the orbit and ocular adnexa

Solitary fibrous tumour (SFT) is an uncommon spindle cell tumour of mesenchymal origin characterised by NAB2-STAT6 gene fusion. Although it was first described in the pleura, it can occur in connective tissue in any part of the body, but rarely presents in the orbit and ocular adnexa. SFT, which is part of the same disease spectrum as other fibroblastic tumours such as giant cell angiofibroma, haemangiopericytoma and fibrous histiocytoma, usually presents as a painless, slow-growing mass in any age group and generally follows a benign course, with a good prognosis after complete excision. However, malignant forms rarely occur. Even for benign tumours a more aggressive clinical behaviour is possible, with relentless infiltrative local growth, frequent recurrence following surgery, and malignant transformation with the potential for metastatic spread. Careful long-term follow-up is essential. The published literature on SFTs of the orbit and ocular adnexa is reviewed, and the aetiology, clinical presentation, epidemiology, radiological features, histopathology, immunohistochemistry, risk stratification, clinical management, and prognosis are discussed, reflecting on our own experience.

Preoperative Endovascular Embolization of Orbital Solitary Fibrous Tumor With 500-700 Micron Tris-Acryl Gelatin Microspheres

The reported experience with preoperative embolization of solid orbital tumors is scarce. Herein, we present a case of a large and hypervascular orbital solitary fibrous tumor (SFT) in which 500-700 µm tris-acryl gelatin microspheres (TAGM) were used for preoperative embolization. A 41-year-old man presented with severe proptosis, palpable mass, restrictive myopathy, exposure keratopathy, and compressive optic neuropathy in the right orbit. Magnetic resonance imaging showed a 65x35x35 mm, diffusely contrast-enhanced tumor in the superior orbit, extending to the apex, and multiple intratumoral vascular flow voids. A diagnosis of SFT was made by incisional biopsy. Endovascular tumor embolization was performed with 500-700 µm TAGM. Two days later, the tumor was entirely removed with minimal bleeding. No embolization- or surgery-related complications and tumor recurrence or metastasis developed during the 42-month postoperative follow-up.

Solitary Fibrous Tumor of the Orbit: A Clinicopathologic Study of Two Cases With Review of the Literature

BACKGROUND/AIM

Orbital solitary fibrous tumor (SFT) is a rare lesion among orbital tumors, which can be misdiagnosed as another mesenchymal tumor. In this study we report two cases of orbital SFT, focusing on the imaging and pathological findings of the vascular structure inside the tumor.

CASE REPORT

A 26-year-old woman and 43-year-old man presented with orbital SFT. The pathological findings revealed a patternless growth pattern of the tumor cells and hemangiopericytoma-like vascularity as well as thickened, dilated blood vessels within the tumor tissue. Tumor cells revealed a diffuse strong positivity for cluster of differentiation 34 (CD34) and signal transducer and activator of transcription 6 (STAT6) in both cases, while B-cell lymphoma 2 (bcl-2) and CD99 were positive in one case. Characteristic findings within the tumor were the arterial components, where a variety of STAT6, CD99 and bcl-2-positive smooth muscle cells were intermingled.

CONCLUSION

Histologically, the tumor tissues might be characterized by not only conventional hemangiopericytoma-like vasculature but also dilated arterial vessels, which were shown to be part of the tumor components.