The Current Status of Solitary Fibrous Tumor: Diagnostic Features, Variants, and Genetics

Intrathoracic solitary fibrous tumor - an international multicenter study on clinical outcome and novel circulating biomarkers

Intrathoracic solitary fibrous tumor (SFT) is a rare disease. Radical resection is the standard of care. However, estimating prognosis and planning follow-up and treatment strategies remains challenging. Data were retrospectively collected by five international centers to explore outcome and biomarkers for predicting event-free-survival (EFS). 125 histological proven SFT patients (74 female; 59.2%; 104 benign; 83.2%) were analyzed. The one-, three-, five- and ten-year EFS after curative-intent surgery was 98%, 90%, 77% and 67%, respectively. Patients age (≥59 vs. <59 years hazard ratio (HR) 4.23, 95 confidence interval (CI) 1.56–11.47, p = 0.005), tumor-dignity (malignant vs. benign HR 6.98, CI 3.01–16.20, p <0.001), tumor-size (>10 cm vs. ≤10 cm HR 2.53, CI 1.10–5.83, p = 0.030), de Perrot staging (late vs. early HR 3.85, CI 1.65–8.98, p = 0.002) and resection margins (positive vs. negative HR 4.17, CI 1.15–15.17, p = 0,030) were associated with EFS. Furthermore, fibrinogen (elevated vs. normal HR 4.00, CI 1.49–10.72, p = 0.006) and the neutrophil–to-lymphocyte-ratio (NLR > 5 vs. < 5 HR 3.91, CI 1.40–10.89, p = 0.009) were prognostic after univariate analyses. After multivariate analyses tumor-dignity and fibrinogen remained as independent prognosticators. Besides validating the role of age, tumor-dignity, tumor-size, stage and resection margins, we identified for the first time inflammatory markers as prognosticators in SFT.

Giant solitary fibrous tumour of the pleura an unpredictable entity: case series and literature review

A small proportion of tumours can undergo malignant transformation. We report a case series of five patients diagnosed with giant solitary fibrous tumours of the pleura. These cases highlight the unpredictable nature of this disease process, with significant variability in clinical course observed, from indolence to aggressive progression. Three patients were found to have malignant disease on explant, with two of these having preoperative imaging and histology suggesting benign pathology. This finding emphasises that accurately differentiating between benign and malignant disease on imaging and/or biopsy has low specificity and sensitivity and cannot be relied upon in guiding the management of these tumours. Patients with solitary fibrous tumours of the pleura should be managed cautiously, owing to the unpredictable and potentially aggressive clinical course. We would advocate the position that all patients with solitary fibrous tumours of the pleura should be managed as if they have malignant disease. Prolonged follow-up is required due to the risk of disease recurrence, even in patients with benign disease.

Identification of novel follicular dendritic cell sarcoma markers, FDCSP and SRGN, by whole transcriptome sequencing

Follicular dendritic cell (FDC)-sarcoma is a rare neoplasm with morphologic and phenotypic features of FDCs. It shows an extremely heterogeneous morphology, therefore, its diagnosis relys on the phenotype of tumor cells. Aim of the present study was the identification of new specific markers for FDC-sarcoma by whole transcriptome sequencing (WTS). Candidate markers were selected based on gene expression level and biological function. Immunohistochemistry was performed on reactive tonsils, on 22 cases of FDC-sarcomas and 214 control cases including 114 carcinomas, 87 soft tissue tumors, 5 melanomas, 5 thymomas and 3 interdigitating dendritic cell sarcomas. FDC secreted protein (FDCSP) and Serglycin (SRGN) proved to be specific markers of FDC and related tumor. They showed better specificity and sensitivity values than some well known markers used in FDC sarcoma diagnosis (specificity: 98.6%, and 100%, respectively; sensitivity: 72.73% and 68.18%, respectively). In our cohorts CXCL13, CD21, CD35, FDCSP and SRGN were the best markers for FDC-sarcoma diagnosis and could discriminate 21/22 FDC sarcomas from other mesenchymal tumors by linear discriminant analysis. In summary, by WTS we identified two novel FDC markers and by the analysis of a wide cohort of cases and controls we propose an efficient marker panel for the diagnosis of this rare and enigmatic tumor.

STAT6 Reliably Distinguishes Solitary Fibrous Tumors from Myofibromas

Solitary fibrous tumors (SFT) and myofibromas (MF) historically have belonged to the same morphologic spectrum and have been lumped together under the nonspecific umbrella term, "hemangiopericytoma" along with other pericytic/myoid tumors. While current evidence shows clear distinction between the two entities, they frequently remain in the same histopathologic differential diagnosis. This diagnostic dilemma especially is common for smaller incisional biopsies from the oral cavity. STAT6 immunohistochemistry (IHC) recently was established as a reliable method to detect solitary fibrous tumor; however, the literature is sparse regarding STAT6 reactivity in MFs. The authors report ten new cases of oral solitary fibrous tumor, discuss histopathologic similarities and differences between the two tumors, and list respective STAT6 IHC expressivity. After IRB approval, 10 cases diagnosed as SFT and 24 cases of MF were collected from the University of Florida Oral and Maxillofacial Pathology Biopsy Service between the years 1994 and 2016. The original hematoxylin and eosin slides and related IHC were reviewed. IHC with STAT6 antibody was performed on all 34 samples, and the findings were analyzed. All cases were from the oral cavity or perioral regions. 10/10 SFTs expressed STAT6 nuclear reactivity, while no cases of MF showed nuclear expression of STAT6. STAT6 is a dependable marker to differentiate SFTs from MFs.

Cutaneous and Superficial Soft Tissue CD34+ Spindle Cell Proliferation

CONTEXT

- Cutaneous and superficial soft tissue spindle cell proliferations with CD34 expression represent a unique heterogeneous group of lesions. They can pose diagnostic challenges for unaware pathologists in their daily practice.

OBJECTIVE

- To review selected entities of CD34⁺ spindle cell proliferations in the skin and superficial soft tissue. The effective diagnostic approaches using clinical, histopathologic, and immunophenotypical findings are discussed within a broad spectrum of differential diagnosis.

DATA SOURCES

- All information used in the article is obtained from published literature by PubMed search and Internet-based search engines. The authors' collective experience and real-life examples are also used.

CONCLUSIONS

- Spindle cell proliferations with CD34 positivity can be worked up to a definitive diagnosis by using clinical, histopathologic, and immunophenotypical findings. Familiarity with these entities helps pathologists make the accurate diagnosis.

Solitary fibrous tumor of the breast: A case report and the review of the literature

Solitary fibrous tumors (SFT) are rare mesenchymal neoplasms. They were first described as spindle-cell tumors originating from the pleura, but they may arise in any anatomical site. SFT of the breast is an exceedingly rare clinical entity. Our literature review yielded only 21 cases reported so far. We describe a case of a SFT of the breast in a premenopausal patient who presented with a gradually enlarging palpable breast mass. Diagnostic evaluation and management are discussed along with a review of the relevant literature. There are no pathognomonic imaging findings of SFT of the breast. Complete surgical resection with clear margins is the gold standard of treatment. Thorough immunohistochemical analysis is crucial to obtain a definitive diagnosis. Although most SFTs run an indolent course, in some cases the clinical behavior can be unpredictable and a long-term follow-up for all patients is therefore mandatory.

[A mysterious pleural lesion: A case report]

A computed tomography scanner first, then a magnetic resonance imaging were performed for chest pain in a 24-year-old woman allowed to find out a 5-cm long and 2-cm large right pleural tumour close to the rachis (T9 and T10) and spindle-shaped. This patient was a smoker and reported a fall down the stairs a few weeks ago. A scan-guided biopsy was decided and microscopic examination revealed a fibrous tissue in which were entrapped regular and non-suspicious alveolar glands. After elimination of differential diagnosis, the most probable hypothesis was that this lesion was due to the traumatism reported by the patient.

Dermatofibrosarcoma protuberans of the breast: A case report

Dermatofibrosarcoma protuberans (DFSP) is a rare malignant tumor of subcutaneous tissue characterized by slow infiltrative growth. The tumor occurs in patients of all ages, with the highest frequency occurring between the second and the fifth decades of age. Genetically, DFSP is characterized by a reciprocal translocation t(17;22)(q22;q13), or more often, as a supernumerary ring chromosome involving chromosomes 17 and 22. Standard treatment of a localized tumor is surgical excision with wide margins. In the present study, a case report of a 43-year-old woman with a growing tumor in the left breast is discussed. The patient underwent breast-conserving surgery. Histological and cytogenetic examinations of the tumor resulted in a diagnosis of DFSP. The clinical and morphological characteristics of the tumor, in addition to the treatment options, were also evaluated.

Solitary Fibrous Tumors of Chest: Another Look with the Oncologic Perspective

Solitary fibrous tumors are mesenchymal lesions that arise at a variety of sites, most commonly the pleura. Most patients are asymptomatic at diagnosis, with lesions being detected incidentally. Nevertheless, some patients present due to symptoms from local tumor compression (eg. of the airways and pulmonary parenchyma). Furthermore, radiological methods are not always conclusive in making a diagnosis, and thus, pathological analysis is often required. In the past three decades, immunohistochemical techniques have provided a gold standard in solitary fibrous tumor diagnosis. The signature marker of solitary fibrous tumor is the presence of the NAB2-STAT6 fusion that can be reliably detected with a STAT6 antibody. While solitary fibrous tumors are most often benign, they can be malignant in 10-20% of the cases. Unfortunately, histological parameters are not always predictive of benign vs malignant solitary fibrous tumors. As solitary fibrous tumors are generally regarded as relatively chemoresistant tumors; treatment is often limited to localized treatment modalities. The optimal treatment of solitary fibrous tumors appears to be complete surgical resection for both primary and local recurrent disease. However, in cases of suboptimal resection, large disease burden, or advanced recurrence, a multidisciplinary approach may be preferable. Specifically, radiotherapy for inoperable local disease can provide palliation/shrinkage. Given their sometimes -unpredictable and often- protracted clinical course, long-term follow-up post-resection is recommended.

Giant Perineal Solitary Fibrous Tumor: A Rare Case Report

Background. Solitary fibrous tumor (SFT) is a fibroblastic mesenchymal tumor that was initially described from the pleura but currently arises at almost every anatomic site. It is usually benign, and surgical resection is curative. SFT involving the perineum is extremely rare. This is the third case report of a perineal SFT in the literature. Case Presentation. We reported an uncommon case of a 64-year-old man presenting with a huge perineal mass that started growing 3 years before his arrival in our service. He was asymptomatic. A contrast-enhanced CT scan revealed a heterogeneous well-circumscribed perineal mass with soft-tissue density. Invasion of the surrounding organs, distal metastasis, and lymph node swelling were absent. The complete resection of mass was done successfully. The specimen was a 23.0 × 14.0 × 8.0 cm encapsulated tumor. Mass weight was 1,170 g. After pathological analysis, we confirmed that the mass was a solitary fibrous tumor. The diagnosis was based on clinical findings and histological morphology and immunohistochemistry study. Conclusion. SFTs are usually indolent tumors with a favorable prognosis. The perineal location is extremely rare. Complete resection of the mass is the treatment of choice.

Encapsulated follicular variant of papillary thyroid carcinoma/noninvasive follicular thyroid neoplasm with papillary-like nuclear features with Spindle Cell Metaplasia: Case report and review of literature

Spindle cell lesions of the thyroid are rare overall, and span a wide clinical spectrum that ranges from spindle cell metaplasia (SCM¹) to anaplastic carcinoma. Their differentiation is only seldom straightforward, and usually requires the integration of the clinical, histological and immunohistochemical data. Only a handful of publications have described cases of SCM in the thyroid and we add to that literature by reporting a unique case of encapsulated follicular variant of papillary thyroid carcinoma/noninvasive follicular thyroid neoplasm with papillary-like nuclear features with SCM. In addition, we review the literature on the relationship between SCM and different thyroid lesions, summarizing the morphological and immunohistochemical features that aid in its differentiation from more aggressive spindle cell proliferations.

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.

Ectopic pleural thymoma in a 49-year-old woman: A case report

Ectopic pleural thymoma is an exceedingly uncommon clinical entity that has only been described sporadically. Because of their peculiar location and variety of histologic patterns manifested, pleural thymomas may be confused with other neoplasms and may cause diagnostic problems clinically, radiologically, and morphologically. We describe the case of a giant left-sided ectopic pleural thymoma, preoperatively suspected to be a solitary fibrous tumor. A complete surgical resection was achieved and a postoperative diagnosis of WHO Type AB, modified Masaoka stage I tumor was attained. Subsequent thymectomy demonstrated unremarkable thymic tissue. The possibility of ectopic thymoma should be considered when the morphology of the lesion reveals a dual population of epithelial cells without significant nuclear atypia and lymphoid cells. Immunohistochemical studies are helpful in supporting the morphologic impression, both by characterizing the epithelial component as thymic in origin and by demonstrating the immature T-cell phenotype of the admixed reactive lymphocytes.

A solitary fibrous tumor with concurrent meningioma at the same site: A case report and review of the literature

The present study describes a case of a solitary fibrous tumor (SFT) concurrent with meningioma in the same anatomical region. The patient was admitted to Tianjin Huanhu Hospital (Tianjin, China) presenting with progressive eyesight impairment, dizziness and right hemiparesis. Cranial magnetic resonance imaging revealed two primary tumors co-occurring at the same site. One lesion was a solid lesion located in the left frontal convex with homogeneous enhancement, and was closely associated with the dura mater; thus, it was suspected that the lesion was a meningioma. The second lesion was cystic and solid with an irregular shape, and was located next to the first tumor; this lesion was believed to be a hemangiopericytoma or astrocytoma. The patient underwent a left temporoparietal craniectomy and a complete excision of the two tumors was achieved. Subsequent pathological examination of the resected tissues confirmed that the two tumors were a secretory meningioma and a SFT, respectively. Immunohistochemistry is important in differentiating SFTs from other tumors. Currently, a total tumor resection is the optimal treatment strategy when managing these rare lesions, often with no requirement for adjuvant post-operative therapy; however, long-term follow-up is essential to detect any signs of recurrence. The possibility of multiple tumors should be taken into consideration when performing clinical examination. To further understand the mechanisms underlying the occurrence of multiple intracranial tumors, further research is required, alongside an increased number of case reports.