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

Occult solitary fibrous tumour of the pleura presenting as recurrent spontaneous pneumothorax

A woman in her 30s, non-smoker, presented at the emergency department two times because of spontaneous pneumothorax. The first episode was treated with small bore catheter drainage, while during the second episode-occurring only 1 week later-thoracoscopic talcage was attempted. The postoperative course was characterised by slow clinical and radiological resolution, and recurrence 3 days after discharge. Eventually, multiportal video-assisted thoracoscopic exploration identified an interfissural solid mass. Resection and further work-up revealed the diagnosis of 'low-risk' solitary fibrous tumour (SFT) stage pT1N0M0. The interdisciplinary tumour board advised no adjuvant therapy. A CT thorax was scheduled in 1 year for follow-up. The patient was discharged without complications and has had no recurrences of pneumothorax at 6 months of follow-up. This report shows that SFT can easily be missed on initial presentation and should be considered in the differential diagnosis of pneumothorax, especially when frequently recurring.

Solitary fibrous tumor occurring at unusual sites: A clinico-pathological series of 31 cases with emphasis on its wide morphological spectrum

Solitary fibrous tumor (SFT) is a relatively rare mesenchymal fibroblastic tumor occurring most commonly in adults with no gender predilection. Although the pathological diagnosis of SFT is usually straightforward, some difficulties may occasionally arise mainly due to the wide morphological spectrum exhibited by this tumor. In the present paper we aimed to evaluate the unusual clinicopathological features in a series of 31 SFTs arising from parenchymal organs, superficial soft tissues and deep soft tissues. Our results emphasize that SFTs may occur anywhere, including unusual sites such as periosteum of the thoracic spine, mesorectal tissue, hepatic hilum, paravescial space, kidney and breast. Moreover, a wide morphological spectrum was observed in tumors included in our series. The most striking morphological features observed included: extensive lipomatous component, myxoid stromal changes, epithelioid cell component, metaplastic mature bone, neurofibroma-like, myxofibrosarcoma-like and pseudoalveolar-like areas. Additionally, multinucleated giant cells and sarcomatous dedifferentiation were also identified. Our paper emphasizes that SFT may occur in unusual anatomical locations and exhibits a wide morphological spectrum. Pathologists must be aware of these features to avoid confusion with other benign and malignant neoplasms that may show overlapping morphological features.

Exploring Solitary Fibrous Tumors at a Tertiary Cancer Center: Clinicopathological and Immunomorphologic Profile

Background Solitary fibrous tumor (SFT) is a distinct fibroblastic tumor that can occur at any anatomical site and can manifest a variety of histopathological features. NAB2-STAT6 gene fusion has recently emerged as a sensitive and specific molecular marker and its surrogate on immunohistochemistry, STAT6 has also displayed considerable efficacy. Nevertheless, its histologic diversity can result in diagnostic challenges, especially when classic features are not apparent. Methods A retrospective study was conducted at a tertiary cancer centre in North India over 3 years to document the clinicopathologic and immunomorphologic profile of SFTs. Immunohistochemical analysis of BCOR and p53 were gauged additionally and patients were stratified according to Modified Demicco and Salas criteria for risk of metastasis. Results Sixteen patients of SFT were identified, affecting middle-aged men and women equally. Though lung/pleura are known to be involved commonly, SFT affects other sites such as the kidney, brain, buccal mucosa, liver, and penis as well. The majority endured localized disease while a lesser number suffered locoregional/distant spread. Two patients revealed features of a malignant profile. Risk stratification according to the Modified Demicco and Salas criteria evinced comparable results. No discernible relationship however was highlighted between the immunohistochemical expression of BCOR, p53, and any significant SFT parameter. Conclusion Although SFTs are very rare substantially benign mesenchymal neoplasms, pathologists must be conversant with their histological diversity and be vigilant of their malignant attributes. The worth of STAT6 immunohistochemistry for precise diagnosis and long-term studies for delineating clinical behavior cannot be overemphasized.

Imaging, pathology, and diagnosis of solitary fibrous tumor of the pancreas: A case report and review of literature

BACKGROUND

A solitary fibrous tumor (SFT) is often located in the pleura, while SFT of the pancreas is extremely rare. Here, we report a case of SFT of the pancreas and discuss imaging, histopathology, and immunohistochemistry for accurate diagnosis and treatment.

CASE SUMMARY

A 54-year-old man presented to our hospital with pancreatic occupancy for over a month. There were no previous complaints of discomfort. His blood pressure was normal. Blood glucose, tumor markers, and enhanced computed tomography (CT) suggested a malignant tumor. Because the CT appearance of pancreatic cancer varies, we could not confirm the diagnosis; therefore, we performed endoscopic ultrasound-guided fine-needle biopsy (EUS-FNB). Pathology and immunohistochemistry were consistent with SFT of the pancreas. The postoperative pathology and immunohistochemistry were consistent with the puncture results. The patient presented for a follow-up examination one month after discharge with no adverse effects.

CONCLUSION

Other diseases must be excluded in patients with a pancreatic mass that cannot be diagnosed. CT and pathological histology have diagnostic value for pancreatic tumors. Endoscopic puncture biopsy under ultrasound can help diagnose pancreatic masses that cannot be diagnosed preoperatively. Surgery is an effective treatment for SFT of the pancreas; however, long-term follow-up is strongly recommended because of the possibility of malignant transformation of the tumor.

Solitary fibrous tumor in the retroperitoneum: A case report

INTRODUCTION AND IMPORTANCE

Solitary fibrous tumor (SFT) is an uncommon mesenchymal tumor that can manifest in a variety of locations, including the retroperitoneum. The most effective standard diagnostic approach and treatment is yet to be determined due to unpredictable behavior of SFT, including retroperitoneal SFT.

CASE PRESENTATION

A 43-year-old female with a retroperitoneal SFT presented with a palpable mass and symptomatology. Surgical exploration disclosed a tumor encompassing the left renal artery and vein, necessitating left nephrectomy and retroperitoneal mass removal. Initial histological examination suggested rhabdomyosarcoma, but subsequent immunohistochemistry confirmed the diagnosis of retroperitoneal SFT. No adjuvant therapy was administered, and there was no detectable mass on follow-up imaging. The patient remained symptom-free.

CLINICAL DISCUSSION

Retroperitoneal SFTs are difficult to diagnose due to their non-specific morphology, thus immunohistochemistry plays a crucial role in confirming its diagnosis. Surgical excision with negative resection margins continues to be the standard treatment. Recurrence rates are low in comparison to other retroperitoneal sarcomas, hence routine chemotherapy or radiation therapy is not advised.

CONCLUSION

This case demonstrates the significance of contemplating SFT as the differential diagnosis of retroperitoneal tumors and the role of immunohistochemistry in confirming the diagnosis. The optimal management strategies for retroperitoneal SFTs should be determined by additional research.

Diagnostics and Treatment of Extrameningeal Solitary Fibrous Tumors

Solitary fibrous tumors (SFT) are rare mesenchymal neoplasms that account for less than 2% of all soft tissue masses. In the latest WHO 2020 Classification of Soft Tissue Tumors, extrameningeal SFT was listed as intermediate (rarely metastasizing) or malignant neoplasms. Due to the lack of characteristic clinical features, their diagnosis and treatment remain challenging. The pathogenesis of SFT is often associated with the presence of fusions of the NAB2-STAT6 gene on the 12q13 chromosome. Cytoplasmic CD34 positive staining is considerably characteristic for most SFTs; less frequently, factor XII, vimentin, bcl-2, and CD99 are present. A key factor in the diagnosis is the prevalent nuclear location of STAT6 expression. Radical resection is the mainstay of localized SFTs. In the case of unresectable disease, only radiotherapy or radio-chemotherapy may significantly ensure long-term local control of primary and metastatic lesions. To date, no practical guidelines have been published for the treatment of advanced or metastatic disease. Classical anthracycline-based chemotherapy is applicable. The latest studies suggest that antiangiogenic therapies should be considered after first-line treatment. Other drugs, such as imatinib, figitumumab, axitinib, and eribulin, are also being tested. Definitive radiotherapy appears to be a promising therapeutic modality. Since standards for the treatment of advanced and metastatic diseases are not available, further investigation of novel agents is necessary.

Solitary fibrous tumor of the tympanic membrane a case report and systematic review

PURPOSE

Otological solitary fibrous tumors (SFT) are exceedingly rare. There has been no report of SFT localized to the tympanic membrane. To report on a rare case of solitary fibrous tumor of the tympanic membrane and provide systematic review of the literature pertaining the demographics and pathophysiology of otological SFTs.

MATERIALS AND METHODS

This review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) reporting guidelines. A search of PubMed, Google Scholar, and Cochrane Library databases was conducted to identify English-language articles on solitary fibrous tumor of the ear, with emphasis on the tympanic membrane, published through 2022. A combination of Boolean operators and the following keywords were included in the search strategy: "solitary fibrous tumor", "tympanic membrane", and "ear".

RESULTS

We found 12 previous reports of solitary fibrous tumors of the ears, none of which were in the tympanic membrane. All cases underwent surgical resection, with or without perioperative embolization, or radiation. There was no evidence of distant diseases in any cases.

CONCLUSIONS

In the context of a tympanic membrane mass with associated pain and hearing loss, our findings suggest that solitary fibrous tumor should be included in the differential diagnosis.

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.

A diagnostic challenge; pelvic solitary fibrous tumor (SFT) mimicking Peri-Anal gastrointestinal stromal tumor (GIST): A case report

Key Clinical Message

The study reports a rare case of pelvic solitary fibrous tumor (SFT) that was initially considered as a peri-anal gastrointestinal stromal tumor due to similar radiologic/pathologic features. SFT diagnosis can be challenging due to its rarity and wide range of diagnoses that must be ruled out precisely.

Abstract

Solitary fibrous tumors (SFTs) are rare tumors that can occur in any part of the body. Although usually benign, malignant SFTs have been reported, especially outside the lungs. Radiology can help with diagnosis, but immunohistochemistry is necessary to distinguish SFTs from other possible diagnoses such as gastrointestinal stromal tumors (GISTs). This study presents a rare case of pelvic SFT initially considered to be a peri-anal GIST, highlighting the importance of accurate diagnosis given the rarity of SFTs and the need to rule out other potential diagnoses.

An update on selected cutaneous (myo) fibroblastic mesenchymal tumors

Cutaneous (myo)fibroblastic tumors constitute a group of tumors with overlapping clinicopathological features and variable biologic behavior. In the present review we focus on the histomorphology, immunohistochemical profile and molecular background of the following entities: dermatofibrosarcoma protuberans (DFSP), CD34-positive fibroblastic tumor (SCD34FT), myxoinflammatory sarcoma (MIFS), low-grade myofibroblastic sarcoma, solitary fibrous tumor and nodular fasciitis. Although some of these entities typically arise in deep-seated locations, they may occasionally present as cutaneous/superficial tumors and might be challenging to recognize. This review covers in depth the latest advances in molecular diagnostics and immunohistochemical markers that have significantly facilitated the correct classification and diagnosis of these neoplasms.

Solitary fibrous tumor of the central nervous system invading and penetrating the skull: A case report

Solitary fibrous tumor (SFT) of the central nervous system is a rare spindle cell tumor of mesenchymal origin. The present study reports the case of a 44-year-old male patient with SFT. Magnetic resonance imaging demonstrated that the majority of the intracranial tumors exhibited uneven low signals on T1-weighted imaging (T1WI) and low mixed signals on T2WI, and there was an enhancement on enhanced scanning. Furthermore, the distal part of the left occipital lobe exhibited hypersignals on T1WI and T2WI, and this was significantly enhanced following enhanced scanning. The lower part of the scalp exhibited low signals on T1WI and high signals on T2WI, and there was no notable enhancement following enhanced scanning. Magnetic resonance spectroscopy demonstrated an elevated choline/creatine peak in the solid part of the tumor. Under the microscope, the tumor exhibited characteristic 'staghorn-shaped' blood vessels. As SFT is difficult to differentially diagnose via imaging, immunohistochemical analysis of CD34, vimentin and signal transducer and activator of transcription 6 was performed for the definitive diagnosis of SFT. Of note, surgical resection was the preferred treatment for SFT; however, due to the rarity of the tumor, subsequent adjuvant therapy and prognosis require further investigation.

Radiation management of a late thoracic metastasis from an intracranial solitary fibrous tumour

Solitary fibrous tumours (SFTs) are a rare soft tissue sarcoma. We present a case of a male patient with an SFT of the right posterior fossa, with a late metastasis to the right lung and chest wall identified 18 years later.A small number of late metastases of SFTs have previously been reported. Metastases are typically managed surgically, although there is limited evidence suggesting that radiotherapy may be effective for primary SFTs.In this case, the patient declined treatment for his metastasised cancer for 5 years. He then only agreed to radiation treatment without surgery, which uniquely resulted in excellent symptom relief and durable local control. This case illustrates the importance of further research on the role of radiation in managing SFTs, the value of long-term follow-up and the necessity of exploring barriers to care.This case also highlights issues regarding barriers to care related to late diagnoses of recurrence in rare tumours. In this case, at the time of recurrence the original tissue blocks were not available for review. The patient had moved to a different province where his former records were not easily accessible, and the original tissue blocks had been discarded. In that jurisdiction, laboratories must keep cytology slides for 5 years, histopathology slides for 10 years and paraffin blocks for 2 years. This contributed to a misdiagnosis of the recurrence as an Ewing sarcoma, resulting in the patient initially declining treatment at the time of disease recurrence, and leading to a long-standing mistrust of his physicians which impacted his decision-making.

Multidisciplinary treatment of giant presacral solitary fibrous tumour: a case report and literature review

Solitary fibrous tumours (SFTs) usually occur at the pleura. Extrapleural sites, particularly giant extrapleural solitary fibromas, are more rarely observed in the clinic, and the clinical diagnosis and treatment of this disease is a focus of attention. Herein, the case of a 43-year-old male patient with giant presacral SFT successfully treated by open surgery, and with a final diagnosis confirmed by postoperative pathology and immunohistochemistry, is reported. The patient was followed-up regularly during 5 years after surgery, with no obvious surgical complications, and no tumour recurrence noted on pelvic magnetic resonance imaging. This case provides clinical information that may help in the diagnosis and treatment of complex SFT.

Peripheral Inflammatory Indexes Neutrophil/Lymphocyte Ratio (NLR) and Red Cell Distribution Width (RDW) as Prognostic Biomarkers in Advanced Solitary Fibrous Tumour (SFT) Treated with Pazopanib

Pazopanib was assessed prospectively in the GEIS-32 phase II study (NCT02066285) on advanced solitary fibrous tumour (SFT), resulting in a longer progression-free survival (PFS) and overall survival (OS) compared with historical controls treated with chemotherapy. A retrospective analysis of peripheral inflammatory indexes in patients enrolled into GEIS-32 was performed to evaluate their prognostic and predictive value. Patients received pazopanib 800 mg/day as the first antiangiogenic line. The impacts of baseline neutrophil/lymphocyte ratio (NLR), platelet/lymphocyte ratio (PLR), and red cell distribution width (RDW) on PFS, OS, and Choi response were evaluated by univariate and multivariate analysis. Metastasis-free interval (MFI), mitotic count, and ECOG were also included as potential prognostic factors. Sixty-seven SFT patients, enrolled in this study, showed a median age of 63 years and a female/male distribution of 57/43. The median follow-up from treatment initiation was 16.8 months. High baseline NLR, PLR, and standardised RDW were significantly associated with worse PFS and OS. NLR, RDW, MFI, and mitotic count were independent variables for PFS, while RDW and ECOG were independent for OS. Further, NLR and mitotic count were independent factors for Choi response. High baseline NLR and RDW values were independent prognostic biomarkers for worse outcome in advanced SFT patients treated with pazopanib.

Solitary Fibrous Tumor of the Adrenal Gland

OBJECTIVES

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Case report: 125I seed implantation for rare malignant solitary fibrous tumor in the pelvic cavity: a case report

Solitary fibrous tumor (SFT) is a rare spindle cell tumor, benign or low-grade malignant, with an extremely low possibility of occurrence of malignant solitary fibrous tumor (MSFT). Surgery is an effective way for treating SFT, but it is often difficult to resect completely due to a large size, with a high recurrence rate and mortality rate after operation. Additionally, SFT is relatively resistant to chemotherapy, and there is a lack of effective systemic drug treatment. These lead to certain difficulties in the treatment of SFT. We report a case of a rare MSFT in the pelvic cavity. With a history of recurrence after two surgeries, this patient underwent surgical removal combined with ¹²⁵I seed implantation at our hospital in the context that the tumor could not be completely removed because it was large and adhered to surrounding tissues; after up to 43 months of progression-free survival (PFS), the patient underwent ¹²⁵I seed implantation alone, and achieved a complete remission, with a PFS up to 35 months. ¹²⁵I seed implantation can be a safe and effective treatment option for unresectable MSFT as well as a potential solution to repeated local recurrence.

Mesentery solitary fibrous tumor with postoperative recurrence and sarcomatosis: A case report and review of literature

BACKGROUND

Solitary fibrous tumors are rare neoplasms of mesenchymal origin. They are often of low malignant potential and rarely metastasize. They frequently arise from the pleura and can occur at any soft tissue site in the body. However, these tumors rarely develop in the mesentery, peritoneal cavity or peritoneum.

CASE SUMMARY

We report on a scarce case of solitary fibrous tumor of the rectal mesentery showing sarcomatosis about 4 years after previous tumor resection. This 69-year-old male had no clinical symptoms but was transferred to our hospital because of a suspected tumor recurrence from follow-up abdominal computed tomography. Tumor markers (CEA, CA 19-9 and CA 125) were within the normal range. Open laparotomy showed sarcomatosis, and pathology confirmed its mesenchymal origin and diagnosis as the solitary fibrous tumor. Our case may be the second recurrent mesentery solitary fibrous tumor reported to date, and the only one with progression to sarcomatosis. There has been no evidence of recurrence in follow-up at the 28^th mo after extensive intra-operative peritoneal lavage and cytoreductive surgery.

CONCLUSION

Although there are few risk factors of cancer recurrence in this patient, careful long-term follow-up after cytoreductive surgery is necessary.

A Giant Solitary Fibrous Tumour of the Pleura

A solitary fibrous tumour of the pleura (SFTP) is a rare pathology, frequently benign in nature, and is usually diagnosed incidentally on imaging. We herein describe the case of a previously fit and well, 35-year-old Caucasian lady, who presented to us with a history of progressively worsening shortness of breath. Her chest X-ray showed a near-complete opacification of the right hemithorax, with displacement of the mediastinum towards the left. This study was supplemented by a computed tomography (CT), which demonstrated a well-circumscribed, non-homogenous mass, occupying the entirety of the right hemithorax. A large, smooth, encapsulated tumour was surgically resected via a posterolateral thoracotomy, measuring approximately 23.1 cm x 21.0 cm x 11.5 cm and weighing 3640 grams. Histopathology confirmed the diagnosis of a benign SFTP with an intermediate malignant potential. At six months, a follow-up CT scan demonstrated no evidence of disease recurrence.

Solitary Fibrous Tumor With Extensive Epithelial Inclusions

OBJECTIVES

Solitary fibrous tumor (SFT) harboring extensive epithelial inclusions is rare and can stimulate a biphasic neoplasm composed of epithelial and stromal elements.

METHODS

Three cases of SFT with extensive epithelial inclusions were retrieved. H&E stain, immunohistochemical stain, and targeted next-generation sequencing were performed.

RESULTS

There were two male patients and one female patient aged 54, 32, and 68 years. All tumors were located in abdominopelvic sites involving the kidney (case 1), omentum (case 2), and prostate (case 3), respectively. Microscopically, all tumors were circumscribed and composed of a background of SFT admixed with randomly embedded glands or cysts, organizing sometimes in a phyllodes-like architecture. The covered epithelium displayed a range of morphologies from simple cystic to stratified and to complex papillary proliferation. Immunohistochemically, both STAT6 and CD34 were expressed in the spindle cells but not in the epithelial inclusions. RNA sequencing revealed fusions involving NAB2~STAT6 in all cases. DNA sequencing demonstrated TERT c.-124C>T mutation in case 1. Prognostic stratification scores were intermediate in case 1 and low in cases 2 and 3.

CONCLUSIONS

SFT with extensive epithelial inclusions represents a rare but potentially underrecognized variant of SFT and shows compatible molecular features with conventional SFT.

Solitary fibrous tumors: Clinical and imaging features from head to toe

Solitary fibrous tumors (SFTs) are rare fibroblastic mesenchymal tumors that are usually benign with variable malignant potential. They can develop in any organ due to their spindle cell origin. The exact etiology of solitary fibrous tumors is unknown. The majority of SFTs are benign with 10-30% of them exhibiting aggressive and malignant features. The aggressiveness of this type of tumor is not associated with its histological features, which makes surgical resection the treatment of choice. We will review the clinical and radiological features and possible differential diagnoses of SFTs according to their anatomical sites following the World Health Organization 2020 classification.

Update on MR Imaging of Soft Tissue Tumors of Head and Neck

This article reviews soft tissue tumors of the head and neck following the 2020 revision of WHO Classification of Soft Tissue and Bone Tumours. Common soft tissue tumors in the head and neck and tumors are discussed, along with newly added entities to the classification system. Salient clinical and imaging features that may allow for improved diagnostic accuracy or to narrow the imaging differential diagnosis are covered. Advanced imaging techniques are discussed, with a focus on diffusion-weighted and dynamic contrast imaging and their potential to help characterize soft tissue tumors and aid in distinguishing malignant from benign tumors.

Miscellaneous Tumours of Bone

There are several tumors that do not easily fit into the specific classifications of primary bone tumors. These tumors include tumors of neural, adipocytic, smooth muscle lineage, and some of uncertain lineage. The pathologic features with recent updates of these tumors are discussed here.

Clinical, Pathologic, and Radiologic Features of Orbital Solitary Fibrous Tumors and Meningiomas

A wide variety of benign and malignant tumors can arise from different structures in the orbital and peri-orbital area, affecting the eye and the optic nerve. This spectrum of tumors includes primary and metastatic carcinomas, lymphomas, melanomas, soft tissue tumors, and primary tumors of the retina, optic disc, and optic nerve. These also extend to relatively rare entities such as solitary fibrous tumor and meningioma of the orbit and optic nerve, which can present with very similar clinical and radiologic features, although the tumor grades, treatment plans, and outcomes can vary widely. In this report, we present two clinical cases of solitary fibrous tumor [central nervous system (CNS) World Health Organization (WHO) grade 2 and 3) and compare their clinical presentation, radiologic and histologic features, treatment, and clinical outcomes to a group of three orbital meningiomas (CNS WHO grade 1 and 2). In the context of these five cases of orbital lesions, we review the current clinical, pathologic, and radiologic literature on orbital tumors, focusing primarily on solitary fibrous tumors and meningiomas, along with an expanded discussion on the diagnostic criteria of both entities, as well as the treatment and prognosis of these lesions.

Omental Solitary Fibrous Tumor: A Rare Tumor at Rare Site

Extrapleural solitary fibrous tumor-hemangiopericytoma is a rare tumor. We present a case of this tumor arising in omentum, which is an extremely rare site. The diagnosis was confirmed by diffuse expression of STAT6 on immunohistochemistry. The tumor was assigned a low-risk category according to recent risk categorization models. The patient was advised close follow-up as the tumor was excised completely. These tumors have the potential for recurrence and metastasis even after surgical excision. However, there are no definitive guidelines for adjuvant treatment due to lack of data.

DFSP of the Breast: Histomorphological, Immunohistochemical, and Molecular Features of a Rare Case in an Unusual Location

We present a case of a 21-year-old female with a vague nontender mass in the lower inner quadrant of the left breast discovered incidentally on chest imaging following trauma. A breast ultrasound demonstrated an 8×6×8 mm irregular hyperechoic mass at the 7 o'clock position of the left breast, 9 cm from the nipple. The mass was graded Breast Imaging Reporting and Data System (BI-RADS) category 4 (suspicious finding). An ultrasound-guided biopsy of the mass showed a proliferation of monotonous spindled cells in a storiform pattern with tapered nuclei with infiltration into the adipose tissue. No normal breast elements were identified in the biopsy. Myofibroblastoma was the first differential diagnosis; however, the characteristic infiltrative pattern of the tumor mandated additional tests including fluorescence in situ hybridization to rule out a dermatofibrosarcoma protruberance (DFSP). Immunohistochemical staining showed positive staining for CD34, which can be positive in myofibroblastoma also. However, fluorescence in situ hybridization demonstrated a platelet-derived growth factor B (22q13.1) gene rearrangement confirming a diagnosis of DFSP. The patient underwent a wide local excision of the DFSP for definitive treatment. She is doing well with no recurrence reported so far, after 15 months of follow-up. Conventional DFSP does not metastasize but is prone to recurrence making wide margins imperative for definitive treatment.

Fascin-1 is associated with recurrence in solitary fibrous tumor/hemangiopericytoma

Fascin-1, an actin-bundling protein, is associated with poor prognosis in patients with various types of human carcinoma. However, research is limited on the role of fascin-1 in sarcoma. Solitary fibrous tumor (SFT) and hemangiopericytoma (HPC) are rare sarcomas derived from the mesenchyme. Although the prognosis of SFT/HPC is generally favorable, fatalities are possible with repeated recurrence and distant metastasis. The current study included a total of 20 Japanese patients, who were diagnosed with SFT/HPC and underwent surgery at Kochi University Hospital from January 2000 to December 2019. The statistical relationship between recurrence and the following variables were examined: Sex, age of onset, tumor origin, tumor size, necrosis, mitosis ≥1/10 high power field (HPF; magnification, x400), Ki-67 >5% and Fascin-1. A significant association was determined between recurrence and necrosis, mitosis ≥1/10 HPF (magnification, x400), Ki-67 >5%, and Fascin-1 ≥‘strongly positive’ (P<0.05). The results demonstrated that Fascin-1 immunostaining may be a highly effective and useful evaluation factor for predicting poor prognosis in patients with SFT/HPC, a fatal sarcoma of humans.

Solitary fibrous tumor: molecular hallmarks and treatment for a rare sarcoma

Solitary fibrous tumor (SFT) is a rare soft tissue sarcoma subtype which mainly affects adults in the fifth and sixth decades of life. Originally part of a spectrum of tumors called hemangiopericytomas, classification has been refined such that SFTs now represent a distinct subtype. The identification of NAB2-STAT6 fusion in virtually all SFTs has further aided to define this rare subgroup. SFTs have a spectrum of behavior from benign to malignant, with evidence suggesting risk of metastases related to age at diagnosis, extent of necrosis, mitotic rate and tumor size. The standard treatment for localized disease is surgical excision with or without radiotherapy. Retrospective and prospective evidence suggests antiangiogenic treatment is effective for unresectable disease. Further translational work is required to understand the biology driving the differential behavior and identify more effective treatments for patients with metastatic disease.

Radiologic-Pathologic Correlation of Primary Retroperitoneal Neoplasms

An earlier incorrect version of this article appeared in print. The online version is correct.

Clinicopathologic and Immunohistochemical Characteristics of Solitary Fibrous Tumor and Its Mimics: A Single-Center Experience

Background

Solitary fibrous tumor (SFT) is a fibroblastic tumor that has been originally reported as a pleural tumor but now has been defined as a tumor that can be seen everywhere in the human body. Histopathologically, many of the fibroblastic tumors can mimic SFT, and immunohistochemistry is necessary for differential diagnosis. Several markers have been used, and recently, STAT6 has been introduced as a diagnostic marker. No research study has been reported from Iran.

Objectives

In this report, we are trying to introduce our experience about the clinicopathologic findings of 35 cases of SFT during the last 10 years from our center with an emphasis on the diagnostic role of STAT6 in this tumor.

Patients and methods

During the last 10 years, we confirmed the diagnosis of 35 cases of SFT in the pathology archives of Shiraz University of Medical Sciences. These 35 cases were considered as cases. All the clinicopathologic findings were also extracted from the clinical charts of the patients. To evaluate the diagnostic role of STAT6, another 35 cases of spindle cell tumors were also extracted from the pathology archives as mimickers of SFT. STAT6 was stained in all of the 70 cases and controls.

Results and discussion

Our experience showed that SFT is more common in middle-aged men with a wide age range, although it is very rare in children. It can be present in every location with a wide size range from less than 1 cm to more than 15 cm. The presence of abnormal staghorn vessels is one of the main diagnostic histopathologic characteristics. STAT6 showed a sensitivity and specificity of 91% and 86% in the diagnosis of SFT. Other markers such as CD99, CD34, and BCL2 have also been considered useful in the differential diagnosis of this tumor, although the diagnostic accuracy seems to be lower than STAT6. High mitosis, presence of necrosis, and atypia are important criteria for predicting malignant and aggressive behavior in SFT. Among 35 cases in our study, 17% showed malignant behavior as recurrent or metastatic tumors.

Conclusion

Solitary fibrous tumor is a common soft tissue tumor that can be seen everywhere and needs careful histopathologic and immunohistochemical evaluation for the correct diagnosis and prediction of aggressive or benign behavior.

Surgical resection of a presacral solitary fibrous tumor with extension to iliac vessels using Karakousis's abdominoinguinal approach: Report of a rare case

Introduction and importance

The solitary fibrous tumor (SFT) is a rare tumor of mesenchymal origin, with a reported incidence of 2.8 cases per 100,000 tumors and with distinctive histopathological and immunohistochemical characteristics. It was initially described as a pleural lesion and subsequently, it was found in different organs and tissues. The abdominoinguinal incision described by Karakousis allows a safe and radical approach for lower quadrants abdominopelvic tumors.

Case presentation

A 47-year-old man was referred to us with a 5-months history of lower backache radiating to the left lower limb. MRI and CT revealed a retroperitoneal mass of 10 cm extending to left iliac vessels. The initial diagnosis corresponded to a sarcomatous retroperitoneal tumor. It was decided to perform an abdominal exploration using Karakousis's approach for surgical resection. The immunohistochemistry and histopathological study revealed neoplasia compatible with a SFT. It was categorized as low risk for developing metastasis and death from disease, according to the new malignancy criteria. Currently, the patient is asymptomatic and disease-free at 19 months after surgery.

Clinical discussion

Most patients with SFTs present symptoms derived from the tumor growth and the compression on adjacent structures with clinical manifestations that are frequently insidious and precede the tumor discovery. The diagnosis is based on histopathological studies. Nonetheless, when they present an extrathoracic location, they represent a diagnostic challenge, due to their variable histological characteristics.

Conclusion

Presacral SFT is a rare entity, with a scant incidence reported regarding this location and long-term treatment. Surgical resection is needed as the immediate treatment.

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A solitary fibrous tumor (SFT) is a rare tumor of mesenchymal origin.

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SFT requires immediate treatment with surgical resection.

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The Karakousis abdominoinguinal incision allows a safe and radical approach.

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The presacral SFT with extension to iliac vessels benefits from the Karakouis approach.

The many faces of solitary fibrous tumor; diversity of histological features, differential diagnosis and role of molecular studies and surrogate markers in avoiding misdiagnosis and predicting the behavior

Background

Solitary Fibrous Tumor (SFT) is a distinct soft tissue neoplasm associated with NAB2-STAT6 gene fusion. It can involve a number of anatomic sites and exhibits a wide spectrum of histological features.

Main body

Apart from diversity in morphological features seen even in conventional SFT, two histologic variants (fat-forming and giant cell-rich) are also recognized. In addition, a malignant form and dedifferentiation are well recognized. Owing to diverse histological features and involvement of diverse anatomic locations, SFT can mimic other soft tissue neoplasms of different lineages including schwannoma, spindle cell lipoma, dermatofibrosarcoma protuberans, liposarcoma, gastrointestinal stromal tumor (GIST), malignant peripheral nerve sheath tumor (MPNST), and synovial sarcoma. SFT is classified as an intermediate (rarely metastasizing) tumor according to World Health Organization Classification of Tumors of Soft tissue and Bone, 5th edition. The management and prognosis of SFT differs from its malignant mimics and correct diagnosis is therefore important. Although SFT expresses a distinct immunohistochemical (IHC) profile, the classic histomorphological and IHC profile is not seen in all cases and diagnosis can be challenging. NAB2-STAT6 gene fusion has recently emerged as a sensitive and specific molecular marker and its IHC surrogate marker signal transducer and activator of transcription 6 (STAT6) has also shown significant sensitivity and specificity. However, few recent studies have reported STAT6 expression in other soft tissue neoplasms.

Conclusion

This review will focus on describing the diversity of histological features of SFT, differential diagnoses and discussing the features helpful in distinguishing SFT from its histological mimics.

Magnetic Resonance Imaging of Orbital Solitary Fibrous Tumors: Radiological-Pathological Correlation Analysis

Background:

Solitary fibrous tumors (SFTs) are rare and can be misdiagnosed because of their various radiological appearances.

Purpose:

To clarify the characteristic MRI findings of SFTs by analyzing their radiological-pathological correlation.

Material and Methods:

Nine consecutive patients with SFT who underwent magnetic resonance imaging (MRI) prior to surgery were analyzed. Eight patients underwent contrast-enhanced MRI, and three underwent dynamic MRI. Radiological-pathological correlation analysis, co-occurrence matrix, run-length matrix, and histogram analysis were performed to assess the relationship between pathological findings T1- and T2-weighted images (T1-WI and T2-WI).

Results:

All nine lesions ranged in size from 20 to 36 mm. Seven lesions were located in the superior portion of the retrobulbar space found outside of the muscle cone, and two lesions in the inferior portion were located within it. No significant correlation was observed between the amount of collagenous tissue and the qualitative evaluation of the signal on T1-WI and T2-WI. Kurtosis on T2-WI was significantly correlated with the amount of collagenous tissue (ρ = –0.97, p < 0.0001) and endothelial cells (ρ = –0.49, p = 0.0479).

Conclusion:

Kurtosis in the histogram analysis on T2WI showed a strong correlation with the amount of collagenous tissue.

The 2020 WHO Classification: What's New in Soft Tissue Tumor Pathology?

The fifth edition of the World Health Organization Classification of Tumors of Soft Tissue and Bone was published in early 2020. The revisions reflect a consensus among an international expert editorial board composed of soft tissue and bone pathologists, geneticists, a medical oncologist, surgeon, and radiologist. The changes in the soft tissue tumor chapter notably include diverse, recently described tumor types (eg, atypical spindle cell/pleomorphic lipomatous tumor, angiofibroma of soft tissue, and CIC-rearranged sarcoma), new clinically significant prognostic information for a variety of existing entities (eg, dedifferentiated liposarcoma and solitary fibrous tumor), and a plethora of novel genetic alterations, some of practical diagnostic relevance (eg, NAB2-STAT6 in solitary fibrous tumor, FOSB rearrangements in epithelioid hemangioma and pseudomyogenic hemangioendothelioma, and SUZ12 or EED mutations in malignant peripheral nerve sheath tumor, leading to loss of H3K27 trimethylation). In this review, we highlight the major changes to the soft tissue chapter in the 2020 World Health Organization Classification, as well as the new chapter on undifferentiated small round cell sarcomas, with a focus on updates in diagnostic categories, prognostication, and novel markers. Recent discoveries in molecular genetics are also discussed, particularly those of immediate utility in differential diagnosis, including protein correlates detectable using immunohistochemistry.

Solitary Fibrous Tumor of the Retroperitoneal Space

A solitary fibrous tumor develops from mesenchymal cells as a pleural neoplasm, but it is also occasionally reported in extrapleural sites. Retroperitoneal tumors are a group of neoplasms located between muscles and the fascia of the posterior abdominal wall and the parietal peritoneum. Their cytology differs from that of urinary tract organs or adrenals. This case report presents a rare solitary fibrous tumor incidentally found during an ultrasound examination. A 54-year-old male underwent urgent surgery for a tumor located in the left retroperitoneal space. The histologic examination confirmed a solitary fibrous tumor with a 5% Ki67 proliferation index, a 1 MF/10 HPF mitotic activity, and CD34-positive immunostains. A solitary fibrous tumor is a rare retroperitoneal tumor. Its symptoms and signs might resemble those of the classical triad of renal cell carcinoma, although the tumor's growth phase is typically asymptomatic. Intraoperative diagnosis of a solitary fibrous tumor strongly recommends radical excision.

Solitary fibrous tumor of bone developing lung metastases on long-term follow-up

Solitary fibrous tumors are rare mesenchymal neoplasms of fibroblastic or myofibroblastic origin. Primary solitary fibrous tumors arising in bone are extremely rare and rarely metastasize. We present a case of solitary fibrous tumor where the diagnosis was delayed due to a failure to recognize the subtle, lytic lesion underlying a fracture of the left humerus. The patient underwent proximal humeral replacement and was followed closely with imaging of humerus and chest. A small lung metastasis was found on CT scan 38 months later and was resected. Two additional small metastases were found and resected 62 months after initial tumor resection. The purpose of this case report is both to highlight the radiologic challenges which can lead to overlooking a lytic lesion underlying a fracture and to show the importance of long-term follow-up in patients with solitary fibrous tumor.

Intracranial malignant solitary fibrous tumor metastasized to the chest wall: A case report and review of literature

BACKGROUND

Solitary fibrous tumor (SFT) is a rare fibroblastic mesenchymal neoplasm that affects spindle cell soft tissues with broad-spectrum biological behavior; it is predominantly benign, and rarely metastasizes. SFT occurs mainly in the tissue structure of the serosa in the pleura and the thorax, and can be found throughout the body, though extra-thoracic localization, including the cephalic region, is un-common. We reported the first case of intracranial malignant SFT metastasized to the chest wall.

CASE SUMMARY

An 81-year-old Japanese man was referred to our hospital due to progressive gait disturbance and appetite loss. His medical history included partial resection due to brain tumor, four times, and 50-Gray radiation therapy at another hospital, starting when he was 74 years old. An unenhanced head computed tomography (CT) scan revealed an 8 cm × 5.1 cm × 6.5 cm mixed-density mass at the left frontal lobe, accompanying a midline shift, and an unenhanced chest-abdomen CT scan revealed a 6 cm × 4.1 cm × 6.5 cm low-density mass in the left chest wall. A CT-guided percutaneous lung biopsy was performed, and the pathological findings were SFT corresponding to brain tumor. Finally, the correct diagnosis of his brain tumor in history of past illness revealed to be SFT, and the unremovable tumor, namely present brain lesions enlarged and metastasized to the chest wall. We established a definitive diagnosis of intracranial malignant SFT metastasized to the chest wall. We notified him and his family of the disease, and offered palliative care. He passed away on the 29^th hospital day.

CONCLUSION

This case suggests the need for careful, detailed examination, and careful follow-up when encountering patients presenting with a mass.

Solitary Fibrous Tumor of Pancreas With Unusual Features: A Case Report

Solitary fibrous tumor (SFT) is an uncommon fibroblastic neoplasm that is most commonly associated with the pleura but has also been reported in almost all anatomic sites. Although the majority of SFTs are benign, few cases follow a malignant clinical course and may recur and/or metastasize after several years of their original occurrence. Only 16 cases of pancreatic SFTs are reported so far, and only one has metastasized to lung and subcutis. Pancreatic SFT resembles more common neuroendocrine tumor and gastrointestinal stromal tumor (GIST) radiographically and is at times almost indistinguishable from GIST histologically. Diagnosis of SFTs particularly, if attempted on biopsied specimens, can be very challenging due to its rare occurrence and nondescript morphology. It is imperative to understand the pathological spectrum of this entity to avoid misdiagnosis. We report a case of pancreatic SFT in a 43-year-old male with some unusual morphologic and immunohistochemical features including pseudoangiomatous growth pattern, a hypercellular area demonstrating nuclear pleomorphism, and only focal positivity for cluster of differentiation (CD)34. These atypical features can pose even more diagnostic challenge by causing additional confusion with other malignancies like dedifferentiated liposarcoma and vascular tumors. The potential diagnostic pitfalls are discussed.

Giant cell-rich extrapleural solitary fibrous tumor: Cytological findings and differential diagnosis of a rare neoplasm

Extrapleural solitary fibrous tumor (ESFT) is a rare neoplasm with a variable biological behavior that may occur almost everywhere in the body, as it has been reported in head and neck, back, retroperitoneum, inguinal region and more. The diagnosis of ESFT may be challenging, especially in case of its morphological rare variants such as giant cell-rich ESFT. Fine-needle aspiration cytology (FNAC) is a rapid, poorly invasive, safe diagnostic technique, which is recently proving useful for the preoperative diagnosis of mesenchymal neoplasms. Herein we report a case of a FNAC diagnosis of giant cell-rich ESFT, focusing on its morphological and immunocytochemical characteristics, and showing how cytology may be an effective tool in the preoperative diagnosis of mesenchymal neoplasms, allowing the correct surgical management of the patient.

Prostate preserving resection of a rare giant peri-prostatic solitary fibrous tumor

Solitary fibrous tumors (SFTs) are rare mesenchymal neoplasms that have been infrequently documented in the prostate. In this case, a 78 year old man experiencing constipation and lower abdominal pain presented with a SFT arising from the prostatic fascia encompassing the dorsal vein complex and left neurovascular bundle. To our knowledge this is the first documented case of an SFT limited to the prostatic fascia and neurovascular tissues of the prostate. Using a prostate sparring approach we have been able to achieve favourable oncological and functional outcome.

Rapidly growing solitary fibrous tumors of the pleura: a case report and review of the literature

A solitary fibrous tumor (SFT) is a rare spindle cell tumor-derived from mesenchymal cells. It may be linked to the fusion of the NAB2-STAT6 gene caused by 12q chromosome rearrangement. It can occur in the connective tissue of any part of the body; however, it is most common in the pleura. Solitary fibrous tumors of the pleura (SFTP) are a persistent painless mass with slow growth. With the increase of the tumor, there will be corresponding compression symptoms. Pleural effusion is rare, and the cytology of pleural effusion is mostly negative. Occasionally, SFTP can induce paraneoplastic syndrome, distant metastasis, and malignant transformation. Lung function may have mild to moderate restrictive ventilation dysfunction. CT is a crucial method for the clinical diagnosis of SFTP. The histopathological features of SFTP are the coexistence of sparse and dense areas. CD34, CD99, Bcl-2, and vimentin are the most valuable immunohistochemical markers.The positive expression rate of STAT6 in benign SFT was even 100%. Adhesion or unclear boundary with surrounding tissues, pleural effusion or calcification, tumors with a maximum diameter greater than 10 cm, invasive growth, uneven density, metastasis or recurrence, paraneoplastic syndrome, moderate to severe cell heterogeneity, high Ki67 proliferation index, and low STAT6 expression suggest SFTP may be a malignant tumor. Gene analysis on next generation sequencing may help reveal the mutation characteristics of SFTP. Complete tumor resection is the gold standard of SFTP. Resectability is the most important prognostic factor. Age, size, mitosis, and necrosis are considered risk stratification factors for prognosis. Fortunately, 80% of SFTP are benign and have anexcellentprognosis but need long-term follow-up.We report a case of rapidly growing tumor with pleural effusion within 9 months, who was surgically treated and is currently under follow-up. And the literature is reviewed.

A Case of Intracranial Solitary Fibrous Tumor/Hemangiopericytoma Repeatedly Misdiagnosed as Hypertensive Intracerebral Hemorrhage

Because solitary fibrous tumor (SFT) and hemangiopericytoma (HPC) contain identical genetic abnormalities, the World Health Organization coined the term SFT/HPC to describe these lesions. Here, we present a rare case of SFT/HPC in a 40-year-old man with massive repeated intracranial hemorrhage (ICH) in right medial temporal lobe. ICHs from a SFT/HPC were repeatedly misdiagnosed as hypertensive ICH by several departments and hospitals over approximately eight months, and the patient underwent inappropriate treatments. The amount of repeated ICH accompanying the tumor has increased significantly compared to the first ICH, which may suggest rapid tumor growth. To avoid misdiagnosis and inappropriate treatment, surgeons should carefully examine all past and current patient-related radiological images and medical records before considering surgery.

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.

The role of needle core biopsies in the evaluation of thymic epithelial neoplasms

Thymic epithelial neoplasms are rare tumors derived from thymic epithelium that most often present as large anterior mediastinal masses. The vast majority of thymic epithelial neoplasms fall under the diagnostic category of thymoma, with a smaller percentage qualifying for a diagnosis of thymic carcinoma. The ability to render a definitive diagnosis on these tumors is generally hampered by their deep location and close proximity to vital structures, which makes biopsy sampling for histopathologic evaluation difficult. In recent years, the trend in medicine has been to opt for the least invasive procedure to obtain tissue samples that, by definition, implies also obtaining smaller and smaller biopsies, resulting in lesser amounts of tissue available for examination. In the mediastinum, the most common modalities for procuring biopsy samples from mass lesions include fine-needle aspiration, percutaneous core needle biopsy and video-assisted thoracoscopic biopsy. In this review, we will deal only with the role and limitations of percutaneous core biopsies in the interpretation of thymic epithelial neoplasms.

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.