Nuclear Expression Of STAT6 Research Articles

Malignant solitary fibrous tumor of the kidney with IGF2 secretion and without hypoglycemia

BackgroundSolitary fibrous tumor (SFT) is a rare fibroblastic mesenchymal tumor that mostly involves the pleura and infrequently involves extra-pleural sites. De novo SFT of the kidney is uncommon, and malignant SFT is extremely rare.Case presentationWe report a case of a 51-year-old man with a large malignant SFT in the left kidney. Pathological examination confirmed the diagnosis of SFT based on typical morphology, nuclear STAT6 expression, and NAB2-STAT6 gene fusion. The malignant subtype was determined by a large tumor size (≥ 15 cm) and high mitotic counts (8/10 high-power fields). KRAS mutation was identified by DNA sequencing. Insulin-like growth factor 2 (IGF2) was diffusely and strongly expressed in tumor cells, however, hypoglycemia was not observed. Hyperglycemia and high adrenocorticotropic hormone (ACTH) concentration were observed one month after surgery. Hormone measurements revealed normal blood cortisol and aldosterone levels, and increased urinary free cortisol level. A pituitary microadenoma was identified using brain magnetic resonance imaging, which may be responsible for the promotion of hyperglycemia.ConclusionsWe report a case of renal malignant SFT with a KRAS mutation, which was previously unreported in SFT and may be associated with its malignant behavior. Additionally, we emphasize that malignant SFT commonly causes severe hypoglycemia due to the production of IGF2. However, this effect may be masked by the presence of other lesions that promote hyperglycemia. Therefore, when encountering a malignant SFT with diffuse and strong IGF2 expression and without hypoglycemia, other lesions promoting hyperglycemia need to be ruled out.

Sinonasal Glomangiopericytoma with Skull Base Involvement: A Diagnostic Dilemma.

Introduction: Glomangiopericytoma (GPC) is a rare type of neoplasm with hemangiopericytoma-like vasculature and perivascular hyalinization of capillary-sized veins. CD34 and S100 protein staining might be positive in a small percentage of GPC. Solitary fibrous tumors (SFTs) present clinically like GPC. However, challenges remain when differentiating GPC from SFT. Case Presentation: A 37-year-old male, smoker, presented with 3 years history of right-sided epistaxis and nasal congestion. He was also complaining of hyposmia but no headaches or visual complaints. On nasal endoscopy, he was found to have a right-sided nasal mass occupying the ethmoid cavity. Computed tomography showed a right sinonasal mass abutting the anterior skull base and magnetic resonance imaging demonstrated a hyperintense, enhancing mass within the right ethmoid cavity, superior septum, and anterior skull base. The patient underwent endoscopic resection with gross total resection and skull base reconstruction. Postoperative pathology initially was thought to be an SFT; however, subsequent STAT6 expression was negative, and therefore GPC diagnosis was confirmed. At the most recent follow-up (6 months), the patient remained free of local disease. Discussion: SFT, unlike GPC, stains strongly for CD34, in this case, due to strong CD34, the diagnosis of SFT was initially made. Nuclear STAT6 expression is highly specific and sensitive for SFT. This later returned as negative; therefore, GPC was confirmed. Conclusion: We present a case of sinonasal GPC with skull base involvement that was treated with endoscopic resection. At the most recent follow-up (6 months), the patient remained free of local disease.

ROLE OF GATA3 AND STAT6 IMMUNOHISTOCHEMISTRY IN CLASSIC HODGKIN LYMPHOMA (CHL) AND NODULAR LYMPHOCYTE PREDOMINANT HODGKIN LYMPHOMA (NLPHL)

Objective: The purpose of our study is to investigate the utility of immunohistochemical expression of GATA3 and STAT6 in differentiating Classic Hodgkin Lymphoma (CHL) from Nodular Lymphocyte Predominant Hodgkin Lymphoma (NLPHL). Material and Methods: We approached database of Shaukat Khanum Memorial Cancer Hospital and Research Centre and selected a total of 79 CHLs and 15 NLPHLs diagnosed either on Trucut biopsy or excision biopsy diagnosed during the time 2020-2021. One slide from each of these 94 cases was stained with GATA3 and STAT6 independently and pattern of staining (either nuclear or cytoplasmic or dual nuclear and cytoplasmic) was accessed. Results: 75/79(95%) cases of CHL were positive for GATA3 staining [60/79(75.9%) cases showed nuclear GATA3 staining, 15/79(18.9%) cases showed both nuclear and cytoplasmic staining] and 4/79(5%) CHL cases were negative for GATA3. 15/15(100%) cases of NLPHL were negative for GATA3[12/15(80%) cases showed no staining and 3/15(20%) cases showed only cytoplasmic blush]. 65/79(82%) cases of CHL were positive for STAT6[17/79(21.5%) cases showed nuclear STAT6 expression, 48/79(60.7%) cases showed both nuclear and cytoplasmic staining], and 14/79(18%) cases of CHL were negative for STAT6 expression [8/79(10%) cases showed only cytoplasmic staining and 6/79(8%) showed neither nuclear nor cytoplasmic staining]. 14/15(93.3%) cases of NLPHL were negative for STAT6[5/79(33.3%) cases showed only cytoplasmic staining and 9/15(60%) cases showed no staining] and 1/15(6.7%) case of NLPHL was positive for STAT6[showed nuclear STAT6 staining]. Conclusion: Nuclear staining of GATA3 and STAT6 either alone or in combination with cytoplasmic staining can be used to differentiate CHL from NLPHL. GATA3 effectively excludes NLPHL with 100% negative predictive value. Keywords: GATA3, STAT6, Classic Hodgkin lymphoma, Nodular lymphocyte predominant Hodgkin lymphoma

Solitary Fibrous Tumor of the Pancreas: Analysis of 9 Cases With Literature Review.

Solitary fibrous tumor (SFT) has been increasingly reported in various anatomic sites. However, it is still extremely rare in the pancreas. Herein, we present the first series of primary pancreatic SFTs. Nine cases of primary pancreatic SFTs were analyzed. The mean age was 60 years (36 to 76y) with no sex predilection. Six tumors were in the head, 3 were in the tail. On imaging studies, tumors were described as a hypervascular mass, 2 revealed cystic areas, and 3 were favored to be neuroendocrine tumors. On biopsy, 2 cases were diagnosed as atypical spindle cell tumor; one was misdiagnosed as suspicious for sarcoma, and another case as metastatic renal cell carcinoma. Two were diagnosed as low-grade sarcoma and low-grade stromal tumor on frozen sections. Grossly, tumors were well-demarcated with a median size of 4cm (0.9 to 15cm). Microscopically, they were composed of ovoid to spindle tumor cells with no significant mitotic activity and were arranged in alternating hypercellular and hypocellular areas. Staghorn-like vessels and entrapped pancreatic parenchyma were also detected within all tumors. Tumor cells revealed diffuse/strong nuclear STAT6 expression in 7 of 8, CD34 in 7 of 9, and bcl-2 in 4 of 4 tested cases. One tested tumor harbored NAB2 - STAT6 fusion. Eight patients with available follow-up data were free of disease at a mean follow-up of 76 months (3 to 189mo). SFT should be considered in the differential diagnoses of mesenchymal neoplasms of the pancreas. Immunohistochemical nuclear STAT6 expression is a characteristic feature of SFT. Primary pancreatic SFTs seem to have favorable biological behavior in our series.

Solitary Fibrous Tumor of the Adrenal Gland.

Solitary fibrous tumor (SFT) is a mesenchymal neoplasm that can arise at various anatomic locations. It is characterized by inv12(q13q13)-derived NAB2::STAT6 fusion, resulting in the nuclear expression of STAT6. Primary SFT of the adrenal gland is rare. We launched a multi-institutional collaboration to comprehend the overarching demographics, clinical and follow-up, macroscopic, microscopic, IHC, and FISH features of 9 patients with SFT of the adrenal gland. We added a series of 9 patients to the collection of adrenal SFTs where the clinicopathologic parameters, including clinical presentation, imaging, histopathology, IHC, molecular profiles, and management and follow-up data, were analyzed comprehensively. A modified 4-variable risk stratification model, including age, tumor size, and necrosis, was applied. Our series consisted of 6 male and 3 female patients, ranging in age from 19 to 64 years (mean, 49.3 years). Abdominal pain (4) and fever with abdominal pain (1) were the presenting symptoms in 5 patients. In the remaining 4 patients, the tumors were detected by abdominal imaging for hypertension and diabetes. The size of the tumor ranged from 2 cm to 10.5 cm in maximum dimension. All tumors exhibited the morphology of a spindle cell SFT with a patternless architecture; 3 had a focal storiform arrangement. STAT6 positivity was observed in all tumors, and 7 were positive for CD34. Surgical resection was the primary modality of treatment. No adjuvant therapy was administered. Follow-up ranging from 7 months to 23 months was available for 7 patients. All were alive without disease recurrence or metastasis. Risk stratification placed 8 (88.9%) patients into a low-risk category and 1 into an intermediate-risk category. This series is the largest of adrenal SFTs to date. These tumors of the adrenal gland are predominantly spindle cell neoplasms with indolent behavior, with a wide age distribution and a slight male preponderance. Combining our cohort with the previously published cases, the majority of tumors fall into the low-risk category for the propensity to develop metastases. Owing to the rarity and age distribution associated with these tumors, the differential diagnosis is wide and requires a systematic approach for ruling out key differential diagnoses aided by STAT6 IHC.

A mesenchymal chondrosarcoma with aberrant nuclear expression of STAT6: a potential diagnostic pitfall

STAT6 is usually considered to be a very sensitive and specific immunomarker for diagnosis of solitary fibrous tumor (SFT), being a surrogate of the NAB2-STAT6 fusion gene identified in most cases of this tumor. STAT6 expression has also been reported in rare cases of other soft tissue tumors, such as low-grade fibromyxoid sarcoma, myxoid/round cell liposarcoma, dedifferentiated liposarcoma and deep fibrous histiocytoma. The aim of this study was to report, for the first time, a case of mesenchymal chondrosarcoma showing diffuse aberrant immunohistochemical expression of STAT6. Molecular biology, showing the HEY1-NCOA2 fusion gene, was crucial to rule out SFT.

Orbital Solitary Fibrous Tumor: Case Report with nuclear STAT6 expression and CD34+ with literature review.

Orbital Solitary Fibrous Tumor: Case Report with nuclear STAT6 expression and CD34+ with literature review.

Results in the treatment of intracranial haemangiopericytomas. Case series

ObjectiveIntracranial hemangiopericytoma (HPC) is a rare central nervous system tumor characterized by its low incidence, high rate of local recurrence and risk of metastasis. The main objectives of this paper are two: to show the results in the treatment of HPC in our institution in the last 20 years and to make a review of the literature on this topic. MethodsRetrospective review that includes patients diagnosed with intracranial solitary fibrous tumor/hemangiopericytoma (TFS/HPC) that have undergone surgery from 1997 to 2017. It includes patients that had nuclear expression of STAT6 (detected by immunohistochemistry) and grade II/III histopathological diagnosis (defined by the World Health Organization in 2016). We collected demographic data, tumor characteristics, treatment and survival of these patients. ResultsA total of 19 patients fulfilled inclusion criteria. The median follow up was 96 months (12–230). The mortality rate was 21% (n = 4). The median follow up survival was 19.16 years. 57.9% of patients presented at least 1 tumor recurrence (n = 11) (recurrences of 6%, 67% y 90% at 1, 5 and 10 years). Five patients presented extracranial metastasis. Patients with tumors <6 cm had greater survival (p < 0.05). ConclusionsA series of patients undergoing TFS / HPC were presented according to the new WHO criteria. Size is a predictor of survival. Currently there are no validated criteria for surgical resection in this pathology. A classification with surgical guidance would be useful.

Intracranial anaplastic solitary fibrous tumor/hemangiopericytoma: immunohistochemical markers for definitive diagnosis.

Intracranial anaplastic hemangiopericytoma (AHPC) is a rare and malignant subset of solitary fibrous tumor/hemangiopericytoma (SFT/HPC) as per the WHO 2016 Classification of Tumors of the Central Nervous System. AHPC portends a poor prognosis and is associated with higher rates of recurrence/metastasis in comparison with SFT/HPC. Accordingly, it is critical to continue to define the clinical course of patients with AHPC and in so doing further refine clinicopathologic/immunohistochemical (IHC) criteria needed for definitive diagnosis. Herein, we describe clinical/histological characteristics of six patients with AHPC. In addition, we reviewed and analyzed the expression of various IHC markers reported within the literature (i.e., a total of 354 intracranial SFT/HPCs and 460 meningiomas). Histologically, tumors from our six patients were characterized by a staghorn-like vascular pattern, mitotic cells, and strong nuclear atypia. Immunohistochemically, all tumors displayed positive nuclear staining for STAT6; other markers, including CD34 and Bcl-2, were expressed only in three patients. Analysis of IHC expression patterns for SFT/HPC and meningioma within the literature revealed that nuclear expression of STAT6 had the highest specificity (100%) for SFT/HPC, followed by ALDH1 (97.2%) and CD34 (93.6%). Of note, SSTR2A (95.2%) and EMA (85%) displayed a high specificity for meningioma. Anaplastic SFT/HPC is a tumor with poor prognosis that is associated with higher rates of recurrence and metastasis in comparison with SFT/HPC. Given that anaplastic SFT/HPC requires more aggressive treatment than meningioma despite of a similar presentation on imaging, it is crucial to be able to distinguish between these tumors.

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 46.8years (median 44.5years; range 18-76years) 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 2.5cm (median 2.6cm). 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 37.2months), but a third patient developed distant bone metastasis at 86.9months. Overall mean follow-up was 73.1months: 9 patients are alive or dead without disease (mean 77.9months), two patients with persistent disease,and one patient with metastatic disease at last follow-up (102months). Incorporating cases sufficiently reported in the literature, a risk prediction model based on age > 45years, tumor size > 3cm, 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.

Results in the treatment of intracranial hemangiopericytomas. Case series.

Intracranial hemangiopericytoma (HPC) is a rare central nervous system tumor characterized by its low incidence, high rate of local recurrence and risk of metastasis. The main objectives of this paper are two: to show the results in the treatment of HPC in our institution in the last 20years and to make a review of the literature on this topic. Retrospective review that includes patients diagnosed with intracranial solitary fibrous tumor/hemangiopericytoma (SFT/HPC) that have undergone surgery from 1997 to 2017. It includes patients that had nuclear expression of STAT-6 (detected by immunohistochemistry) and gradeII/III histopathological diagnosis (defined by the World Health Organization in 2016). We collected demographic data, tumor characteristics, treatment and survival of these patients. A total of 19 patients fulfilled inclusion criteria. The median follow up was 96 months (12-230). The mortality rate was 21% (n=4). 57.9% of patients presented at least one tumor recurrence (n=11) (recurrences of 6%, 67% y 90% at 1, 5 and 10years). Five patients presented extracranial metastasis. Patients with tumors <6cm had greater survival (P<.05). A series of patients undergoing SFT/HPC were presented according to the new WHO criteria. Size is a predictor of survival. Currently there are no validated criteria for surgical resection in this pathology. A classification with surgical guidance would be useful.

Intracranial Solitary Fibrous Tumor/Hemangiopericytoma: A Clinicoradiological Poorly Recognized Entity- An Institutional Experience.

Intracranial solitary fibrous tumors (SFTs) and hemangiopericytomas (HPCs) are rare nonmeningothelial mesenchymal tumors sharing fusion of NGF1-A binding protein 2 (NAB2) and signal transducers and activators of transcription (STAT6.).The WHO classification of central nervous system (CNS) tumors (2016) highlights that molecular confirmation of NAB2/STAT6 fusion or immunohistochemical nuclear expression of STAT6 is mandatory for the diagnosis of SFT/HPC.Herein, we present a series of four cases of SFT/HPC of the brain, which mimicked other CNS tumors both clinically and radiologically. This is a retrospective study over a period of two and a half years. Out of the 156 operated cases of brain tumors, four patients (2.56%) were diagnosed with SFT/HPC. The clinicoradiological details with the surgical procedure were retrieved from the archived hospital records. All cases were males, of which three were in their 5th decade while one was a 14-month-old baby. Two cases were primary and the rest were recurrent.The location of tumors was extra-axial left cerebellotentorial,clivaldural-based,left cerebellar, and in the left frontoparietal region,respectively. The clinical impression was meningioma in three cases,while it was primitive neuroectodermal tumor (PNET) /atypical teratoid/rhabdoid tumor (ATRT) in one case.With the detailed histomorphology and immunohistochemistry, the final diagnosis was anaplastic hemangiopericytoma(WHO grade III) for all the cases. During our follow-up, one patient died with the disease, while the rest are doing well. SFT/HPC should be kept in the differential diagnosis of all dura-based hypervascular masses, especially in recurrent cases, due to its aggressiveness and high recurrence rate.

STAT6 immunohistochemical expression in meningeal-based tumors: Diagnostic of solitary fibrous tumor/hemangiopericytomas

Background: Updated 2016 WHO classification of central nervous system tumors has unified solitary fibrous tumor (SFT) and hemangiopericytoma (HPC) as a single entity (SFT/HPC), Grading from I to III, in view of common genetic alteration namely fusion of NAB2 and STAT6 genes. Aim: This study aims to evaluate the role of STAT6 immunohistochemical expression in a cohort of meningeal-based tumors and its correlation with other pathological parameters. Materials and Methods: Sixty-two meningeal-based tumors were studied including 40 HPC/SFT (1 Grade I, 29 Grade II and 10 Grade III), 14 meningiomas (2 Grade I, 10 Grade II, 2 anaplastic meningiomas), three meningeal sarcoma, and five cases with features suspicious for SFT/HPC. The expression pattern of STAT6 and other histological findings were noted. Results: Nuclear or nuclear + cytoplasmic STAT6 positivity was seen in 40/40SFT/HPC (100%), diffuse in 30 and focal in 10 cases. Only 1/14 cases of meningioma (7.1%) showed weak nuclear positivity. All cases of meningiomas and 2/3 cases of meningeal sarcoma showed cytoplasmic positivity. Of the five suspicious HPC cases, four showed diffuse strong nuclear STAT6 positivity, based on which they were confirmed as HPC. Interestingly, of the 40 STAT6 positive SFT/HPC, five showed epithelial differentiation (AE1/AE3 and/or epithelial membrane antigen [EMA]). CD34 was negative in 4/36 SFT/HPC. CD34 was focally positive in 3/5 suspicious HPC cases, two of which were focally EMA positive as well, and both cases showed nuclear STAT6 positivity. BCl2 was negative in 5/27 SFT/HPC, all of which were nuclear STAT6 positive. Conclusions: Nuclear expression of STAT6 can serve as a highly sensitive and specific adjunctive diagnostic marker for meningeal-based SFT/HPC, especially in cases with nonconventional histology and immunohistochemical profile, where meningioma or high-grade meningeal sarcoma forms a diagnostic dilemma.

PLEURAL-BASED LUNG MASS WITH AN UNUSUAL PRESENTATION

SESSION TITLE: Disorders of the Pleura 2 SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: 10/09/2018 01:15 pm - 02:15 pm INTRODUCTION: Primary tumors of the pleura are rare. Majority of the tumors are benign. About 10–20% of the cases reported in the literature are malignant. We present a case of a patient with non specific symptoms and radiological findings consistent with a mass of pleural origin. CASE PRESENTATION: 44 year old African American male, presented with symptoms of productive cough, fever and left sided pleuritic chest pain since the last two months. He was recently incarcerated and released two weeks prior to presentation. He was a former smoker of 20 pack years. PPD and HIV test done within the last one year were normal. On physical examination, he had a fever of 102.2F, heart rate of 127/min, and respiratory rate 22/min. Chest auscultation revealed bilateral expiratory wheezing. Labs showed a normal complete blood count and metabolic panel. TB Gold quantiferon was less than 0.01 IU/ml. Respiratory virus panel was positive for rhinovirus. Initial Chest X ray showed a relatively well demarcated round mass in the left mid-lung with minimal displacement of the carina to the right. CT Chest confirmed the presence of a 12.0 x 14.6 x 13.1 cm pleural based lung mass with atelectasis of the left upper lobe and mass effect on the left hilar structures. Patient underwent a CT guided biopsy of the mass. Pathology revealed atypical cells with a low to moderate degree of pleomorphism. Immunohistochemistry revealed expression of CD 34 and diffuse nuclear expression of STAT6. Patient underwent surgical resection of the mass with partial pleurectomy. Intraoperative findings revealed large chest wall mass attached to the anterior parietal pleura. Post-operative course was unremarkable. Surgical pathology confirmed the presence of a malignant solitary fibrous tumor. DISCUSSION: Solitary fibrous tumors of the pleura (SFTP) are rare neoplasms of mesenchymal origin believed to arise from sub mesothelial connective tissue. SFTP is common in the fifth and sixth decades of life compared with SFTs arising intra-abdominally or in soft tissue. There is no sexual predilection. Evidence of a genetic predisposition or a relationship to exposure to asbestos or tobacco have not been demonstrated. The most common presenting symptoms are non-specific and include cough, chest pain and dyspnea. Paraneoplastic syndromes may be occur and present with clubbing, pulmonary osteoarthropathy secondary to secretion of hyaluronic acid, and refractory hypoglycemia due to secretion of insulin like growth factor II. Our patient presented with symptoms of an upper respiratory tract viral infection and non specific symptoms consistent with SFTP .Surgical resection is the mainstay of treatment in both benign and malignant variants. CONCLUSIONS: SFTP are rare. They may present with non specific symptoms.The prognosis for patients with SFTP is generally favorable with a 5-year overall survival rate ranging from 79 to 100%. Reference #1: 1. Solitary fibrous tumors of the pleura.Cardillo G1, Lococo F, Carleo F, Martelli M.Curr Opin Pulm Med. 2012 Jul;18(4):339-46. https://doi.org/10.1097/MCP.0b013e328352f696 Reference #2: Solitary fibrous tumor of the pleura.Robinson LA.Cancer Control. 2006 Oct;13(4):264-9 DISCLOSURES: No relevant relationships by MUHAMMAD ADEEL, source=Web Response no disclosure on file for Ashish Arora; No relevant relationships by Bilal Bangash, source=Web Response No relevant relationships by Jeff Kwon, source=Web Response No relevant relationships by Safal Shetty, source=Web Response

STAT6 expression in spindle cell lesions of the breast: An immunohistochemical study of 48 cases

The diagnosis of spindle cell lesions of the breast parenchyma is challenging. Some of these lesions share the expression of CD34, posing differential diagnostic problems, especially in core biopsies. Recently, antibodies against the STAT6 C-terminal, are being used in paraffin-embedded tissues as a surrogate for identifying the NAB2–STA6 fusion gene which is considered a specific molecular marker for solitary fibrous tumor. Accordingly, we investigated the expression of STAT6 in a large series of uncommon spindle cell tumor-like and tumor lesions occurring primarily in the breast parenchyma. We collected 10 classic-type myofibroblastomas, 9 desmoid-type fibromatosis, 6 spindle cell metaplastic carcinoma, 5 benign fibroblastic spindle cell tumors, 3 solitary fibrous tumors, 7 pseudoangiomatous stromal hyperplasias, 2 reactive spindle cell nodules, 1 leiomyoma, 1 spindle cell lipoma, 1 case of inflammatory pseudotumor, 1 nodular fasciitis, 1 myxoma and 1 dermatofibrosarcoma protuberans. A diffuse and strong nuclear STAT6 expression was restricted only to solitary fibrous tumors, while the other lesions were negative or showed only weak cytoplasmic expression. The present study confirms that the demonstration of a diffuse and strong STAT6 nuclear staining is very helpful in distinguishing solitary fibrous tumor from other spindle cell mimics arising in the breast.

Solitary fibrous tumour of the female genital tract: a clinicopathological analysis of 25 cases.

Solitary fibrous tumour (SFT) is an uncommon spindle cell neoplasm of fibroblastic origin, first described as a tumour of the pleura and now well established at extrapleural sites. However, SFT in the female genital tract is rare and therefore not fully characterised. Here, we describe a series of 25 SFTs arising throughout the gynaecological tract, including the vulva (14 cases), vagina (one), cervix (one), uterus (six), ovary (two), and fallopian tube (one). The tumours showed classic histology as well as known variant morphological features, including a fatty component, diffuse stromal hyalinisation, myxoid stroma, and giant-cell angiofibroma-like features. Eleven (11/25, 44%) were considered to be histologically malignant on the basis of mitotic counts of ≥4 per 10 high-power fields. Follow-up data were available for nine (3-56months; mean 25months). Six patients are alive with no evidence of disease, and three are alive with disease. Both SFT and other spindle cell lesions of the gynaecological tract were stained for STAT6. Ninety per cent of SFTs showed nuclear expression of STAT6. The majority of other tumour types were negative for STAT6, except for a subset of inflammatory myofibroblastic tumours (1/3; 33%), fibroma/thecoma (3/56; 5%), and sclerosing stromal tumour (1/3; 33%), which showed weak/focal staining. Gynaecological SFT can be diagnosed reliably with careful morphological evaluation and judicious use of immunohistochemical stains, and should be considered in the diagnostic workup of spindle cell tumours of unclear lineage in the female genital tract.

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.

Solitary fibrous tumour of the tongue: a series of four cases.

Solitary fibrous tumour is a soft tissue tumour of mesenchymal origin. It was first described in the pleura and has since been reported in many anatomical locations. Thirteen cases in the tongue have hitherto been reported. A positive CD34 result has traditionally been used to confirm the diagnosis, although this is often non-specific to solitary fibrous tumour. To date, nuclear STAT6 expression has not been reported in solitary fibrous tumour of the tongue. This paper presents a further four cases of solitary fibrous tumour of the tongue, the largest series to date. Clinical, histopathological and immunohistochemical findings are detailed, including nuclear STAT6 expression. All four cases were positive for CD34; two cases showed nuclear expression of STAT6. The tumours were excised completely and there have been no recurrences in at least one year. Solitary fibrous tumour should be considered as a differential diagnosis for tongue swellings, with the potential to recur.

Immunohistochemical Expression of Nuclear β-Catenin and STAT-6 in a Solitary Fibrous Tumor of the Soft Palate: A Case Report and Review of the Literature

The solitary fibrous tumors (SFT) are rare tumors in the head and neck region and there have been only 5 cases reported in the literature in the soft palate. The current paper presents a unique case of a 62-year-old male with TFS arising in the soft palate. The tumor was highly cellular, composed of bland looking haphazardly arranged spindle cells. The signal transducer and activator of transcription (STAT)-6 and nuclear β-catenin were reactive by immunohistochemistry (IHC). The current case highlights the importance of the STAT-6 and the β-catenin as IHC markers to make a differential diagnosis with other entities. In summary, the paper presents the first reported case of a SFT of the soft palate in a male patient with nuclear expression of STAT-6 and β-catenin.

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

AimsTo characterise clinicopathological features and clinical outcomes of the genitourinary tract solitary fibrous tumours, incorporating NAB2-STAT6 gene fusion status.MethodsThe presence of the molecular hallmark NAB2-STAT6 gene fusion and for the...