Hemangiopericytoma. An analysis of 106 cases

Rare Encounter: Giant Hemangiopericytoma of Thigh in a Young Male

A rare tumor called hemangiopericytoma develops from the pericytes, the cells that surround blood vessels. They frequently grow slowly and might be asymptomatic initially. Although they can develop anywhere in the body, these tumors are most frequently found in the head, pelvis, and legs. This uncommon tumor originates in soft tissues like fat, muscles, tendons, nerves, blood vessels, and other fibrous tissues. The tumor in adolescence can be benign or malignant; it frequently develops in the bones but has the potential to metastasize to the lungs. Imaging tests, such as MRIs or CT scans, are commonly used in diagnosis to determine the location and size of the tumor. We present a case of a 23-year-old male who complained of swelling in his left thigh that had persisted for two years. He underwent multiple biopsies which were inconclusive until wide local excision of the swelling was done. On histopathology, the excised tumor was suggestive of hemangiopericytoma. The patient was advised of radiotherapy for completion of the treatment.

A case report of sinonasal glomangiopericytoma: An important reminder to always collect specimen

OBJECTIVES

To present a case report of sinonasal glomangiopericytoma (GPC) in a female patient in her thirties and to highlight the importance of collecting pathology specimens even in routine sinus surgery cases.

METHODS

A case report detailing the diagnosis of GPC in a female in her thirties, including her initial presentation, treatment, and follow-up, along with a brief review of the literature.

RESULTS

Pathology of the collected specimen revealed sinonasal GPC along with chronic rhinosinusitis. Immunohistochemistry was positive for SMA, beta-catenin, and cyclin D1; and negative for STAT6, ERG, pankeratin, SOX10, and S100.

CONCLUSION

This diagnosis expands the knowledge around the demographic profile of GPC patients. GPC should be included in the differential diagnosis of sinonasal masses, even in younger patients. The case highlights the importance of collecting the entire pathology specimen in all cases, even of ones that seem routine and benign.

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.

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 76 y) 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 4 cm (0.9 to 15 cm). 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 189 mo). 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.

Single Institution Experience With Sinonasal Glomangiopericytoma: A Case Series

Introduction: Sinonasal glomangiopericytoma (GPC) is an uncommon neoplasm, accounting for less than 0.5% of all sinonasal tumors. It is characterized as having low malignant potential, with complete surgical excision representing optimal treatment. Presenting symptoms are typically due to mass effect and vascularity of this tumor, often including unilateral nasal obstruction or epistaxis. Accounts of this tumor in the literature remain sparse. Methods: Single institution retrospective review. Results: Six cases of sinonasal GPC were identified from a review of the electronic medical records spanning from 2009 through 2021. Age at diagnosis ranged from 48 to 67 years, with a gender distribution of 5 males and 1 female. Most subjects presented with unilateral sinonasal obstruction of variable duration. Each underwent endoscopic resection of the mass with negative margins, and no adjuvant therapy was pursued. Pathologic specimens demonstrated a vascular patterned tumor with spindled cells surrounding vessels and were positive for smooth muscle actin and negative for cytokeratin. Active post-surgical follow-up ranged from 11 months to 10 years. All patients were without endoscopic evidence of recurrence, and 2 had post-operative imaging which showed no evidence of disease. Conclusions: This review of 6 cases of sinonasal GPC represents the largest known series of this rare pathology in the literature to date. Based on our experience, and in agreement with the available literature, this disease is reliably managed with complete surgical excision. Adjuvant therapy can be avoided in otherwise uncomplicated cases. Although rare, GPC should be considered in the differential diagnosis of all vascular sinonasal tumors.

Orbital Primary Solitary Fibrous Tumor: A Proposed Recurrence Risk Prediction Model Based on 92 Cases

Orbital primary solitary fibrous tumors (OPSFTs) are rare. To further characterize the clinical and pathological features of OPSFTs, 92 cases of OPSFT were analyzed to develop a risk prediction model. OPSFTs were equally distributed between males (n = 45) and females (n = 47) with a mean patient age of 40.8 years (median 39 years; range 5-70 years) at initial diagnosis. The mean tumor size was 2.79 cm (median 2.5 cm). Microscopically, the tumor cells were irregularly arranged in spindle, ovoid, or round shapes with varying amounts of collagen and branching blood vessels. Immunohistochemical staining showed positive STAT6 nuclear expression in all cases, loss of CD34 expression in seven cases, and a mean Ki-67 label index of 5.25% (range 1%-30%). All patients were initially surgically resected and had a median follow-up of 99 months: 33 patients recurred, 6 of whom presented with multiple recurrences and 1 with distant metastases. A predictive model for the risk of recurrence based on tumor size, mitosis, Ki-67 label index, and dominant constituent cell (DCC) was developed based on our results. In conclusion, OPSFTs are rare but can be reliably diagnosed based on characteristic morphological features and STAT6 immunohistochemistry. The rate of local recurrence of orbital tumors tends to be higher than the rate of distant metastases, which can be predicted by a risk stratification model specific to orbital tumors. Long-term clinical follow-up is recommended as advanced disease is common.

Endoscopic Excision of Sino Nasal Hemangiopericytoma

Hemangiopericytomas (HPCs) are rare vascular tumours originating from extra capillary cells called Zimmermann's pericytes. Only 5% of these lesions occur in the Sino nasal cavity. Sino nasal HPCs have a benign course with a high recurrence rate ranging from 9.5 to 50%. A radical surgical resection is considered the gold standard treatment either via external approach (lateral rhinotomy or Caldwell-Luc) or endoscopic approach. Three cases of Sino nasal hemangiopericytomas were treated at our institute. All these cases were operated via endoscopic approach. We are reporting their diagnostic work-up and the therapeutic management as case series. We also discuss epidemiological, clinical, morpho-pathological and radiological characteristics of this tumoral pathology. A treatment plan is also elucidated which may help to develop a long term treatment protocol for these lesions.

Hemangiopericytoma an Incidental Parotid Swelling: a Rare Case Report

Hemangiopericytoma of the parotid gland is a very rare presentation in the head and neck region. It occurs mainly in the lower extremities, retroperitoneum, and pelvis. Here we reported a case of 14-year female patient present with painless swelling of the right cheek over the parotid region since 5 years.

Sixteen-Year Follow-Up in a Cavernous Sinus Hemangiopericytoma: Improved Outcomes over Radiotherapy Advances

Intracranial hemangiopericytomas are rare tumors, accounting for 1% of all central nervous system malignancies. This tumor is considered at high risk of local and also distant metastases. Surgical excision is the gold standard for treatment, but it is seldom curative by itself. Adjuvant radiotherapy is often recommended. We report an overview and update of the available literature on one such rare but aggressive mesenchymal tumor, using the case of a 46-year-old woman affected by hemangiopericytoma of the cavernous sinus surgically removed and treated with adjuvant radiotherapy at our institution. After seven years, the patient underwent a local recurrence and was treated with exeresis and Gamma Knife radiotherapy. Sixteen years after the initial diagnosis, she is still well with stable disease.

Clinicopathologic characterization and assessment of prognostic factors for intraabdominal solitary fibrous tumors involving the gastrointestinal tract and liver

Solitary fibrous tumors (SFT) are rare mesenchymal neoplasms with a potential to metastasize in 10-30% of cases. Several risk models have been designed to predict tumor behavior at the pleura and extrapleural sites. Intrabdominal SFTs primarily involving the gastrointestinal tract (SFTGI) and liver (SFTL) are rare. We analyzed a series of SFTGI and SFTL to describe the clinicopathologic features and evaluate prognostic factors. The cohort included 33 males and 25 females, with a median age of 58.5 years and a mean tumor size of 15.6 cm. Patients with SFTL were predominantly older females compared to patients with SFTGI. By univariate analysis, high mitotic count (> 4/10 HPF), tumor size, tumor necrosis, and nuclear pleomorphism were associated with both disease-specific survival (DSS) and metastasis-free survival (MFS) (p < 0.05). Tumor location (SFTL vs. SFTGI) also predicted MFS (p = 0.026). Only very high mitotic count (> 9/10 HPF) predicted local recurrence-free survival (LFS, p = 0.001). Further analysis showed that all adverse histologic parameters (necrosis, hypercellularity, pleomorphism) correlated with high mitotic grade (> 4/10 HPF) (p < 0.05). On multivariate analysis, only mitosis predicted DSS (p = 0.023), MFS (p = 0.01), and LFS (p = 0.017). Validation of the 3 risk models (mDemicco, Salas, Pasquali) showed variable associations with DSS, MFS, and LFS, while a simplied 3-tiered risk model based on mitosis (0-4, 5-9, > 9/10 HPF) performed well in predicting all risks. Our results suggest that prognostication of SFTs is mainly associated with mitotic activity, supporting the use of mitosis (> 4 and/or > 9/10 HPF) for tumor grading and risk stratification at specific locations.

Isolated hemangiopericytoma of the conjunctiva

PURPOSE

To report a unique presentation of hemangiopericytoma and discuss the clinical course, pathological features, and management of this tumor.

OBSERVATIONS

An otherwise healthy 54-year-old Caucasian female presented with a painless conjunctival mass. The lesion gradually enlarged over a three-week period and was unresponsive to corticosteroid treatment. The mass was surgically removed, and histopathologic findings were consistent with hemangiopericytoma.

CONCLUSIONS AND IMPORTANCE

Conjunctival hemangiopericytoma should be considered in patients with conjunctival lesions unresponsive to medical management. Surgical excision is diagnostic and therapeutic and is the strongest predictor of clinical course. Incompletely excised lesions are at a greater risk of local recurrence and subsequent metastasis. Given the neoplasm's malignant potential, patients should be followed in the outpatient setting.

Hemangiopericytoma: Conducts and perioperative management of an extent sinonasal tumor in a Jehovah's Witnesses patient - Case report

Background

Hemangiopericytomas (HPCs) are rare tumors derived from mesenchymal cells with pericyte differentiation. About 5% of head and neck HPCs occur in the nasal cavity and paranasal sinuses. Due to its rarity, rich vascularity and variable biological behavior, its management is a challenge in itself.

Case

We report a case of sinonasal HPC in a Jehovah's Witness patient and discuss the obstacles and care related to the restrictions and therapeutic challenges involved in the approach to the patient. The patient was successfully treated by endoscopic endonasal approach with all per‐operative care and restrictions being respected and attended.

Conclusions

The management of HPC by itself involves challenges and when associated with other restrictive conditions attention and care are required.

Novel Therapeutic Options for Solitary Fibrous Tumor: Antiangiogenic Therapy and Beyond

SFT is an ultrarare mesenchymal ubiquitous tumor, with an incidence rate <1 case/million people/year. The fifth WHO classification published in April 2020 subdivided SFT into three categories: benign (locally aggressive), NOS (rarely metastasizing), and malignant. Recurrence can occur in up to 10-40% of localized SFTs, and several risk stratification models have been proposed to predict the individual risk of metastatic relapse. The Demicco model is the most widely used and is based on age at presentation, tumor size, and mitotic count. Total en bloc resection is the standard treatment of patients with a localized SFT; in case of advanced disease, the clinical efficacy of conventional chemotherapy remains poor. In this review, we discuss new insights into the biology and the treatment of patients with SFT. NAB2-STAT6 oncogenic fusion, which is the pathognomonic hallmark of SFT, is supposedly involved in the overexpression of vascular endothelial growth factor (VEGF). These specific biological features encouraged the successful assessment of antiangiogenic drugs. Overall, antiangiogenic therapies showed a significant activity toward SFT in the advanced/metastatic setting. Nevertheless, these promising results warrant additional investigation to be validated, including randomized phase III trials and biological translational analysis, to understand and predict mechanisms of efficacy and resistance. While the therapeutic potential of immunotherapy remains elusive, the use of antiangiogenics as first-line treatment should be considered.

Large hemangiopericytoma of the shoulder: A case report

Introduction. Hemangiopericytoma is a rare tumour derived from the pericytes, contractile spindle cells that surround the capillaries and postcapillary venules. The tumour is found equally among males and females. Case report. We reported a case of a 63-year-old female who presented a giant painful mass on her right shoulder that occurred one year before admission. Limited range of motion and a sense of tingling along the affected arm was present also. An irregular, oval-shaped mass, dark red in colour, with signs of necrosis, was 14 cm in maximum diameter. Routine laboratory analysis showed results within the range of referenced values. Lung X-ray and ultrasonographic examination of the abdomen showed no signs of secondary tumour deposits, and no osteomuscular lesions in the affected region. Ultrasonographic examination of the neck and right axillary region showed no signs of regional metastases. The surgical excision of the entire tumour was performed, with the associated subcutaneous tissue and a part of fascia underneath. Results of the histopathological analysis confirmed the diagnosis of hemangiopericytoma. The specimen showed no signs or elements of the neoplastic tissue on the edges of the resection lines. Three years after the operation, there were no signs of tumour relapses, regional or systemic metastases. Conclusion. Considering that there are no official clinical guides and protocols for hemangiopericytoma management, as well as the occurrence of cutaneous and subcutaneous heman-giopericytomas is exceptionally rare, more extensive research in this field and more described cases are needed to gain a better understanding of the issue.

Solitary fibrous tumor of thoracic cavity, extra-thoracic sites and central nervous system: Clinicopathologic features and association with local recurrence and metastasis

Published risk stratification models of solitary fibrous tumor (SFT) have been associated with distant metastases outside the central nervous system (CNS), but have not been studied for tumors occurring in the CNS. In a retrospective review, we identified 72 cases of solitary fibrous tumor or hemangiopericytoma (HPC) diagnosed between January 2011 and December 2020 at our institution. The tumors involved the central nervous system (N = 17), thoracic cavity (N = 28), and extrathoracic sites (N = 27). The risk of local recurrence, distant metastasis, or death at 5 years was 57% (95% CI 23%, 76%) in the CNS, 24% (95% CI 2%, 41%) in the thoracic cavity, and 13% (95% CI 0%, 25%) in extrathoracic sites. By contrast, the risk of distant metastasis or death at 5 years was 13% (95% CI 0%, 29%) in CNS primaries, 5% (95% CI 0%, 14%) in thoracic primaries, and 14% (95% CI 0%, 27%) in extrathoracic primaries. Using the published 3- and 4-variable risk stratification models by Demicco et al., we retrospectively assessed our cases for risk of local recurrence, distant metastasis, and death. For tumors outside the CNS, we show that three- and four-variable risk stratification models were associated with recurrence-free survival in addition to the previously known association with distant metastasis (all P < 0.05). In contrast, inside the CNS, we show that neither risk model is a significantly associated with clinical behavior, and that WHO grade is likely the best available prognostic tool, though none of the differences were significant. The lack of significant differences can be likely explained by the younger median age (47 years vs 61 years) and smaller median tumor size (3.5 cm vs 5.6 cm), downgrading the risk stratification scores in CNS compared to non-CNS primaries. In conclusion, existing risk stratification models of SFT are not associated with clinical behavior for tumors arising inside the CNS, but are associated with local recurrence in addition to distant metastasis outside the CNS.

Histological background of dedifferentiated solitary fibrous tumour

AIMS

Dedifferentiation is a histological phenomenon characterised by abrupt transition of histology to a sarcomatous component with high-grade malignant potential in solitary fibrous tumour (SFT). The authors histologically reviewed SFT cases to reveal the histological background of dedifferentiated SFTs.

METHODS

Clinicopathological and histopathological findings of 145 SFT cases were reviewed. Immunohistochemical staining and genetic analysis were also performed.

RESULTS

The non-dedifferentiated components showed a cellular component in 45 of 145 (31%), high mitotic rate (≥4/10 high-powered field) in 12 of 145 (8.2%) tumours, necrosis in 7 of 145 (4.8%) tumours, multinodular growth pattern in 39 of 132 (29.5%) available tumours and intratumoural fibrous septa in 37 of 131 (28.2%). Immunohistochemically, the non-dedifferentiated components were positive for CD34 in 128 of 141 (90.7%), bcl-2 in 101 of 133 (75.9%), nuclear pattern of β-catenin in 64 of 127 (50.3%) and p16 in 22 of 140 (15.7%). Loss of Rb protein expression was detected in 17 of 110 (15.4%) cases. Statistically, cellular component, multinodular structure, p16 overexpression and Rb protein loss were significantly associated with dedifferentiation. Moreover, cellular component and multinodular structure were significantly associated with p16 overexpression and Rb protein loss. All the non-deddifferentiated components showed wild type of p53 expression. The dedifferentiated components of all 10 dedifferentiated tumours presented positivity for p16 in 9 of 10 (90%) and mutational type of p53 in 5 of 10 (50%). Loss of Rb protein expression was detected in 6 of 10 (60%).

CONCLUSIONS

The authors propose that cellular or multinodular transformation may be associated with dedifferentiation. They also suggest that cellular and multinodular transformation may be associated with p16 overexpression and Rb downregulation.

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.

Successful multidisciplinary treatment of Doege-Potter syndrome: hypoglycaemia caused by paraneoplastic IGF-2 production by a metastatic haemangiopericytoma

Hypoglycaemia due to insulin-like growth factor (IGF)-2 secretion is a paraneoplastic complication of malignancy with significant morbidity that can often go unrecognised due to its uncommon presentation. We report on a case of a 51-year-old man with metastatic haemangiopericytoma presenting with refractory hypoglycaemia, requiring continuous dextrose 10% infusion while in hospital. IGF-2 levels were significantly elevated, in keeping with a rare entity associated with solitary fibrous tumours, known as Doege-Potter syndrome. The patient was managed using uncooked cornstarch in conjunction with debulking of the hepatic tumour burden with bland IR-guided transarterial embolisation, and eventual surgical resection to treat his non-islet cell tumour hypoglycaemia (NICTH). The case highlights this rare paraneoplastic phenomenon that should be included in the differential for hypoglycaemia, especially if a history of a solitary fibrous tumour is elicited. Our case is the first to document a successful approach to treating the hypoglycaemia using preoperative transarterial bland embolisation.

Solitary Fibrous Tumor in the Perianal Region: Report of Two Cases With an Atypical Location

A solitary fibrous tumor (SFT) is a mesenchymal neoplasm of spindle cells, initially described in the pleura. The World Health Organization (WHO) classifies the solitary fibrous tumor as a neoplasm with intermediate biological potential. Diagnostic images are essential for the diagnostic and therapeutic approach in this entity. The standard of treatment for this type of lesion is surgical resection with oncological margins larger than 1 cm. The solitary fibrous tumors located in the perianal, perineal, and pelvic regions are infrequent and represent a challenge in the clinical approach, mainly because the manifestations are nonspecific. Given the low incidence of this type of neoplasm, we present two cases of SFT in the perianal region managed in a high-complexity hospital.

Malignant solitary fibrous tumor of the greater omentum: A case report and review of literature

BACKGROUND

Malignant solitary fibrous tumors (SFTs) account for 15%-20% of all SFTs, and malignant SFTs arising from the greater omentum are extremely rare. Most malignant SFTs of the greater omentum are diagnosed via pathological examinations after surgery. In this study, we report a case of malignant omental SFT and review the published literature on this rare malignancy.

CASE SUMMARY

A 64-year-old female presented with an abdominal mass, and underwent exploratory surgery, during which a huge tumor originating from the greater omentum and intraperitoneal implants were identified and resected. The results of the pathological examination, immunohistochemistry staining, and gene sequencing led to the diagnosis of malignant SFT of the greater omentum. The patient died one and a half years later due to tumor recurrence and metastasis.

CONCLUSION

This is the first report of the application of gene sequencing in the diagnosis of malignant SFTs of the greater omentum.

Clinical Outcomes of Patients with Metastatic Solitary Fibrous Tumors: A Japanese Musculoskeletal Oncology Group (JMOG) Multiinstitutional Study

BACKGROUND

Although the unpredictable malignant behavior of solitary fibrous tumors (SFTs) has been recognized, the clinical features and prognosis of metastatic SFTs have not been well documented due to the extreme rarity of these cases. The aim of this study is to investigate the clinical features, prognostic factors, and optimal management of patients with metastatic SFTs.

PATIENTS AND METHODS

Sixty patients with metastatic SFT were retrospectively reviewed. Univariate and multivariate analyses were performed to identify the factors associated with survival. Time to next treatment (TNT) was used to evaluate the effects of various chemotherapy regimens.

RESULTS

A total of 34 male and 26 female patients (median age 55 years, range, 23-87 years) were included in the study. The median follow-up period after metastasis was 32 months (range 1-126 months). Tumor location and local recurrence were correlated with late metastasis. The 3- and 5-year overall survival rates were 72.7% and 49.2%, respectively. Primary tumor location, number of metastases, and metastasectomy were significantly associated with survival. Metastasectomy was the only significant variable on multivariate analysis. The TNT was significantly different among the various regimens.

CONCLUSIONS

Patients with metastatic SFTs had relatively longer survival periods compared with those with other metastatic soft-tissue sarcomas. Tumor location and number of metastases was associated with survival. Surgical resection of the metastatic lesions offers the best chance of survival, however further studies are warranted to define patients who would benefit from metastasectomy, and the most effective chemotherapeutic regimen for patients with metastatic SFTs remains unknown.

Hemangiopericytoma: Incidence, Treatment, and Prognosis Analysis Based on SEER Database

Background

Hemangiopericytomas are rare tumors derived from pericytes surrounding the blood vessels. The clinicopathological characteristics and prognosis of hemangiopericytoma patients remain mostly unknown. In this retrospective cohort study, we assessed the clinicopathological characteristics of hemangiopericytoma patients, as well as the clinical usefulness of different treatment modalities. Material and Methods. We collected the clinicopathological data (between 1975 and 2016) of hemangiopericytoma and hemangioendothelioma patients from the Surveillance, Epidemiology, and End Results (SEER) database. Incidence, treatment, and patient prognosis were assessed.

Results

Data from 1474 patients were analyzed in our study cohort (hemangiopericytoma: n = 1243; hemangioendothelioma: n = 231). The incidence of hemangiopericytoma in 2016 was 0.060 per 100,000 individuals. The overall survival (OS) and cancer-specific survival (CSS) did not differ between patients with hemangioendothelioma and those with hemangiopericytoma (P = 0.721, P = 0.544). The tumor grade had no effect on the OS of hemangiopericytoma patients. Multivariate analysis revealed the clinical usefulness of surgery in hemangiopericytoma patients (HR = 0.15, 95% confidence interval: 0.05-0.41, P < 0.001). In contrast, radiotherapy did not improve OS (P = 0.497) or CSS (P = 0.584), and chemotherapy worsened patient survival (P < 0.001). Additionally, the combination of surgery and radiotherapy had a similar effect with surgery alone on hemangiopericytoma patient survival (OS: P = 0.900; CSS: P = 0.156). Surgery plus chemotherapy provided a worse clinical benefit than surgery alone (P < 0.001).

Conclusions

Our findings suggested that hemangiopericytoma had a similar prognosis with hemangioendothelioma. Surgery was the only effective treatment that provided survival benefits in hemangiopericytoma patients, while the clinical usefulness of adjuvant chemotherapy or radiotherapy was limited.

Malignant solitary fibrous tumour of the prostate: four cases emphasising significant histological and immunophenotypical overlap with sarcomatoid carcinoma

Solitary fibrous tumour (SFT) is well-described in the urinary tract, but malignant examples are rare. We studied our experience with high grade malignant SFT of the prostate to address the degree of histological and immunophenotypical overlap with sarcomatoid carcinoma and prostatic stromal sarcoma. Four cases were identified from the surgical pathology consultation archives. All available H&E stained sections were reviewed. Immunostains for STAT6, CAM5.2, NKX3.1, PAX-8, GATA3, high molecular weight cytokeratin (34BE12), p40, and p63 were performed on available material. Each case was evaluated by three separate SFT prognostic risk models based on clinicopathological features, and for features of 'dedifferentiated SFT'. The patient's ages were 49, 55, 69, and 73 years. Three presented with symptoms of benign prostatic hyperplasia and one with haematuria. Tumour sizes were 5, 9, 13, and 13 cm. Mitotic rate ranged from 6 to 20 mitoses per 10 high power fields, and two cases showed abrupt transition from conventional SFT to areas with marked nuclear pleomorphism/anaplasia (i.e., 'de-differentiation'). Immunophenotypically, all four cases had strong and diffuse nuclear reactivity for STAT6. For other markers, three of three had both focal PR and GATA3 nuclear expression (up to 30% of cells). One case with 'dedifferentiated' features showed expression of multiple epithelial markers, including EMA (focal), high molecular weight cytokeratin (focal), p63, and p40. In summary, malignant SFT may rarely occur in the prostate and may closely mimic sarcomatoid carcinoma or prostatic stromal sarcoma, both histologically and immunophenotypically. Consideration of the diagnostic possibility of malignant SFT, recognition of unexpected GATA3 and PR expression, and utilisation of monoclonal STAT6 immunohistochemistry facilitate appropriate diagnosis at this unusual anatomical site.

Sarcoma metastasis to the pancreas: experience at a single institution

Background

Reports of metastatic sarcoma to the pancreas are limited. We reviewed the clinicopathologic characteristics of such cases.

Methods

We reviewed 124 cases of metastatic tumors to the pancreas diagnosed at Asan Medical Center between 2000 and 2017.

Results

Metastatic tumors to the pancreas consisted of 111 carcinomas (89.5%), 12 sarcomas (9.6%), and one melanoma (0.8%). Primary sarcoma sites were bone (n=4); brain, lung, and soft tissue (n=2 for each); and the uterus and pulmonary vein (n=1 for each). Pathologically, the 12 sarcomas comprised 2 World Health Organization grade III solitary fibrous tumors/hemangiopericytomas, and one case each of synovial sarcoma, malignant solitary fibrous tumor, undifferentiated pleomorphic sarcoma, osteosarcoma, mesenchymal chondrosarcoma, intimal sarcoma, myxofibrosarcoma, myxoid liposarcoma, rhabdomyosarcoma, subtype uncertain, and high-grade spindle-cell sarcoma of uncertain type. The median interval between primary cancer diagnosis and pancreatic metastasis was 28.5 months. One case manifested as a solitary pancreatic osteosarcoma metastasis 15 months prior to detection of osteosarcoma in the femur and was initially misdiagnosed as sarcomatoid carcinoma of the pancreas.

Conclusions

The metastatic sarcoma should remain a differential diagnosis when spindle-cell malignancy is found in the pancreas, even for solitary lesions or in patients without prior history.

Solitary fibrous tumor involving the pancreas: report of the cytologic features and first report of a primary pancreatic solitary fibrous tumor diagnosed by fine-needle aspiration biopsy

INTRODUCTION

Solitary fibrous tumor (SFT) of the pancreas is rare, with only 16 reported cases in English studies. The cytologic features of pancreatic SFT have not been well described. We report 2 cases of SFT (1 primary and 1 metastatic) involving the pancreas and discuss the cytomorphologic findings, including the first primary SFT of the pancreas specifically diagnosed using cytology.

MATERIALS AND METHODS

The cases of 2 patients with a diagnosis of SFT of the pancreas from material obtained via fine needle aspiration (FNA) are reported. Clinical information was retrieved from the patients' medical records. The FNA cytology slides, previous relevant surgical pathologic findings, and findings from subsequent pancreatic resections were reviewed.

RESULTS

Of the 2 patients, 1 had had secondary involvement of the pancreas from a primary central nervous system SFT, and 1 had had a primary pancreatic SFT diagnosed by FNA. Immunohistochemistry for STAT6 was crucial for establishing the diagnosis using FNA.

CONCLUSIONS

We have reported 2 cases of SFT involving the pancreas, including the first reported case of primary pancreatic SFT diagnosed preoperatively using FNA. Metastatic SFT from central nervous system primaries should be considered when diagnosing SFT of the pancreas.

Seminal Vesicle Tumor Microenvironment

Primary diseases of the seminal vesicles (SV) are very rare entities.Nonneoplastic lesions of the seminal vesicles include amyloidosis, inflammation, calcification and calculi, radiation-induced changes, and basal cell proliferation.Seminal vesicles are frequently involved by tumors originating elsewhere, in particular by prostatic adenocarcinoma, urothelial carcinoma, and rectal adenocarcinoma. On the contrary, primary tumors of the seminal vesicles are rare. Among these, the most common is seminal vesicle adenocarcinoma. To date, less than 100 cases have been reported in literature. Morphologically, primary SV adenocarcinoma is described as a papillary or sheetlike growth architecture, with trabecular and glandular patterns, composed by hobnail tumor cells, frequently with mucinous differentiation. On the contrary, mesenchymal tumors include benign lesions such as leiomyoma, schwannoma, fibroma, paraganglioma, solitary fibrous tumor, cystadenoma, and mixed epithelial and stromal tumors (MEST).Cystadenoma is a rare benign tumor, while MESTs are biphasic tumors with stromal and benign epithelial components. Histological features such as stromal atypia, mitotic activity, nuclear pleomorphism, and tumor necrosis distinct MEST in low-, intermediate-, and high-grade tumors.In recent years, multiple studies reported a link between tumorigenesis and tumor microenvironment. In this regard, the molecular mechanisms connecting prostate cancer (PCa) progression and the host microenvironment have been described and include extracellular matrix (ECM), myofibroblasts, cancer-associated fibroblasts (CAFs), neuroendocrine cells, adipose tissue, and the immune-modulatory cells. Of note, only one study evaluated the influence of seminal vesicle's tumor microenvironment (SVME) on prostate cancer cells so far. Besides, in vivo experiments in NOD/SCID mice clarified the influence of SVME on PCa progression. As such, the injection of PC3 cells into the prostate or the SV resulted in different tumor aggressiveness, and the incidence of retroperitoneal lymph node metastases was significantly higher in mice models receiving SV injection. These findings demonstrated that SVs (rather than the prostate) offer a stimulating tumor microenvironment for growth and invasion of prostate cancer cells.

Histological and molecular features of solitary fibrous tumor of the extremities: clinical correlation

Solitary fibrous tumor is a rare mesenchymal neoplasm that exhibits a broad spectrum of biological behaviors. Few studies relative to clinical-pathologic features and predictive factors have been reported, all involving a mixed population of tumors occurring at different anatomic sites. In this study, we described a cohort of 41 patients with solitary fibrous tumor of the extremities and evaluated the prognostic role of clinical and histological features, presence of C228T and C250T mutations at the TERT promoter region, and NAB2-STAT6 fusion variants. Patients were stratified according to the latest risk stratification model proposed by Demicco. The two patients with metastasis at presentation were in the high-risk group; the one with metastasis after surgery was classified in the intermediate-risk group. TERT promoter mutations were detected in 9 out of 38 DNA available. All patients with metastasis were characterized by a TERT promoter mutation. TERT promoter mutation was associated with mitoses > 4 per high-power field (p = 0.001), necrosis (p = 0.049), and size > 10 cm (p = 0.031). NAB2-STAT6 fusion variants were detected in 27 out of 41 cases without any prognostic value. In conclusion, we confirmed that the patients with solitary fibrous tumor of the limbs have a better prognosis than other solitary fibrous tumors, with a very low percentage of metastatic events. Besides, our data support an association between TERT promoter mutations and histologically malignant features, suggesting a possible molecular role in stratifying patients into intermediate- to high-risk tumor.

Clinicopathological review of solitary fibrous tumors: dedifferentiation is a major cause of patient death

Solitary fibrous tumor (SFT) is a soft-tissue neoplasm of intermediate malignant potential, presenting a wide histopathological spectrum. Poorer prognosis of hemangiopericytoma of the central nervous system (CNS), hypoglycemic SFT, and dedifferentiation are well-known characters of SFT, but their clinical significance were not demonstrated enough by large-sized study. Here, the clinicopathological features of SFTs are reviewed and the relationship between genetics and clinicopathological features is examined using 145 SFT cases. All cases were STAT6 IHC-positive and/or NAB2-STAT6 fusion gene-positive. Tumor location was classified into three categories: 30 pleuropulmonary, 96 non-pleuropulmonary/non-central nervous system (CNS), and 18 CNS tumors. The tumor developed recurrence in 21 of 93 available cases (22.5%), metastasis in 11 of 93 (11.8%), and tumor death in 9 of 93 (9.6%). Hypoglycemia occurred in 2 primary tumors and 1 metastatic tumor among 63 reviewable cases, and dedifferentiation occurred in 10 cases (6.8%) including 6 primary tumors, 2 recurrent tumors, and 2 metastatic tumors. Recurrence was positively associated with CNS location (p = 0.0109) and hypoglycemia (p = 0.001); metastasis was positively associated with CNS location (p = 0.0231), hypoglycemia (p < 0.0001), and dedifferentiation (p < 0.0001), while metastasis was negatively correlated with pleural location (p = 0.0471). Tumor death was positively associated with male sex (p = 0.0154), larger size (p = 0.0455), hypoglycemia (p < 0.0001), and dedifferentiation (p < 0.0001). Multivariate analysis revealed independent statistical significance of dedifferentiation for overall survival (p = 0.0467). Exon variant of the fusion gene had no statistical correlation with clinical outcome. In conclusion, dedifferentiation is a major prognostic factor of SFT, and specific location such as cerebromeningeal and intra-abdominal site and hypoglycemia also had a high risk for unfavorable prognosis.

Haemangiopericytoma/Solitary Fibrous Tumour of Mandible: An Uncommonness in the Oral Cavity

Among the bewildering variety of neoplasms occurring in the head and neck region, few are unique to the oral cavity which are quite challenging to diagnose. Due to the rarity of these tumours, it is the practicing oral pathologists' accountability to confirm some of these neoplasms with or without special investigative modalities to rule out the differential diagnosis histopathologically. One in the group of such tumour prevails haemangiopericytoma aka. solitary fibrous tumour (HPC/SFT). The management of these tumours is purely histopathologically driven, since the surgical procedure is dependent on the histological diagnosis. This neoplasm is histologically very difficult to confirm as benign or malignant without the use of immunohistochemical markers. We report such a rare case of a 54-year-old female patient, histopathologically confirmed diagnosis of HPC/SFT with CD34 positivity for documentation in the literature.

Spinal location is prognostic of survival for solitary-fibrous tumor/hemangiopericytoma of the central nervous system

BACKGROUND

Prior studies have highlighted infratentorial tumor location as a prognostic factor for solitary fibrous tumor (SFT) and hemangiopericytoma (HPC) of the central nervous system (CNS), and spinal location is considered a positive prognostic factor for other tumors of the CNS. While SFT/HPC of the CNS is known to frequently arise from the spinal meninges, there are no case series that report outcomes for spinally located CNS tumors, and their prognosis in relation to intracranial and other CNS-located tumors is unknown.

OBJECTIVE

To investigate outcomes for patients with SFT/HPC of the spinal meninges.

METHODS

The Surveillance, Epidemiology, and End-Results Program was used to identify patients with SFT/HPC within the CNS from 1993-2015. We retrospectively analyzed the relationship between tumor location (spinal vs. Brain and other CNS) and survival.

RESULTS

We identified 551 cases of CNS SFT/HPC, 64 (11.6%) of which were primary tumors of the spinal meninges. Spinal tumors were more likely than brain and other CNS tumors to be SFT vs. HPC (37.5 vs. 12%, p < 0.001), benign (42.2 vs. 20.3%, p < 0.001), and less than 5 cm (53.1 vs. 35.7%, p < 0.001). The 10-year survival rates for spinal and brain/other CNS tumors were 85 and 58%, respectively. Median survival time was significantly longer for spinal tumors (median survival not reached vs. 138 months, p = 0.03, HR = 0.41 [95% CI 0.18-0.94]). On multivariable analysis, spinal tumor location was associated with improved survival over tumors located in the brain and other CNS (HR = 0.36 [95% CI 0.15-0.89], p = 0.03).

CONCLUSION

Spinal tumor location is associated with improved survival in patients with SFT/HPC of the CNS. Larger institutional studies are necessary to characterize the relationship between tumor location and other relevant factors such as presentation and amenability to gross-total resection and adjuvant radiotherapy. Future studies exploring optimal management of spinally located tumors are also needed.

A novel mouse model of hemangiopericytoma due to loss of Tsc2

Hemangiopericytoma (HPC) is a rare vascular tumor, which is thought to originate from pericytes. However, no direct evidence for the cell of origin has been found, and the mechanism of HPC tumorigenesis is poorly understood. Here we report that loss of the tumor suppressor gene Tsc2 in pericytes using a FoxD1 promoter driven cre allele (Foxd1tm1(GFP/cre) Amc, FoxD1GC) leads to the formation of HPC in multiple sites. Tsc2ffFoxD1GC mice had stunted growth with seizures and tail and hind limb tremor with a median survival of 110 days. They also showed recombination in brain, spinal cord, tongue, liver, intestine and skeletal muscle. Distinctive perivascular tumors consisting of cells with oval nuclei and scant cytoplasm were identified in multiple sites in all Tsc2ffFoxD1GC mice. Immunohistochemistry staining showed a high expression of phospho-S6-S240/244, a hallmark of activated mTORC1, as well as pericyte markers NG2 and vimentin in these tumors. In summary, we demonstrate that loss of Tsc2 in pericytes generates HPC, the first mouse model of HPC reported.

Hemangiopericytoma of Gingiva in a 4-Year-Old Child: A Rare Case Report

A hemangiopericytoma is a type of soft tissue sarcoma that originates in the pericytes in the walls of capillaries which was characterized in 1942. It is commonly seen in the age group of 5th-6th decades of adults and only 5-10% of cases occur in children with extreme rare occurrence in head and neck region (16%). A rare case of hemangiopericytoma in a 4-year-old female patient is presented here and its clinical, histopathological and immunohistochemically features are discussed. Though surgical resection remains the mainstay, excisional biopsy was primarily performed to reach the final diagnosis. Even in the follow-up phase of 1 year, no recurrence or no metastatic changes were observed.

Gastric Solitary Fibrous Tumor Causing Upper Gastrointestinal Bleeding

We present an 81-year-old woman with remote breast cancer who presented with melena and hemorrhagic shock requiring intensive care hospitalization. Endoscopic evaluation showed a 5-cm pedunculated gastric mass with ulceration and friability. She underwent sleeve gastrectomy for definitive treatment of her bleeding. Pathology was consistent with a solitary fibrous tumor (SFT). There are only a few reported cases of gastric SFTs presenting with gastrointestinal bleeding. If a large brown/tan bleeding mass is identified on upper endoscopy, SFT should be considered.

Mesenchymal Neoplasms of the Genitourinary System: A Selected Review with Recent Advances in Clinical, Diagnostic, and Molecular Findings

Mesenchymal neoplasms of the genitourinary (GU) tract often pose considerable diagnostic challenges due to their wide morphologic spectrum, relative rarity, and unexpected incidence at GU sites. Soft tissue tumors arise throughout the GU tract, whether from adventitia surrounding or connective tissues within the kidneys, urinary bladder, and male and female genital organs. This selected article focuses on a subset of these lesions, ranging from benign to malignant and encompassing a range of patterns of mesenchymal differentiation, where recent scholarship has lent greater insight into their clinical, molecular, or diagnostic features.

Very rare localization of a retroperitoneal hemangiopericytoma revealed by lumbosciatalgia: A case report

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Hemangiopericytoma is a rare vascular tumor representing about 1% of all vascular tumors and approximatively 5% of all soft tissues sarcomas.

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Retroperitoneal hemangiopericytoma is a rare location.

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The radiologic feature suggests the diagnosis but the pathologic findings associated to immune histochemistery remain the only tool to confirm the diagnosis.

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Surgical excision is the most preferred treatment as it helps in relieving the symptoms as well as confirm the diagnosis.

Introduction: Hemangiopericytoma is a rare vascular tumor representing about 1% of all vascular tumors and approximatively 5% of all soft tissues sarcomas that arises from the pericytes of Zimmerman surrounding capillaries and postcapillaries vessels. Retroperitoneal hemangiopericytomas are rare among the localisations as it usually occurs in lower and upper extremities.

Presentation of case: We present a case of 31-year-old man with a well-defined retro peritoneal mass measuring about 105 × 73 × 83 mm at right lower quadrant of the abdomen anterior to right psoas muscle. Intraoperatively, an large mass measuring 10 × 8 cm was found arising from the retro peritoneum. A monobloc excision was performed. The postoperative course was uneventful. Histopathological examination with immune histochemistry revealed that tumoral cells were positive for desmin, CD34, smooth muscular antigen. Final diagnosis of hemangiopericytoma was made. On the last follow up at one year, he was symptom free.

Discussion: Hemangiopericytoma is a rare tumor. It takes origin from pericytes presenting as intervals along the walls of capillaries and post-capillary venules. Retroperitoneal hemangiopericytoma is a rare location. It is often discovered at late course, and can be revealed by various symptoms with the compression of the adjacent organs by the tumor Surgical resection should be considered in symptomatic cases or in case of diagnostic dilemma.

Conclusion: Retroperitoneal hemangiopericytoma can be benign but it should be treated the same way as aggressive tumors. It requires a careful and long term follow up.

Vascular tumours of the liver: a particular story

Vascular tumours of the liver represent an underrated chapter of medical and surgical hepatology. These tumours cover a wide spectrum ranging from the frequent and most benign hepatic haemangioma (HH), via the rare and intermediately aggressive hepatic epithelioid haemangioendothelioma (HEHE) to the rare and most malignant hepatic haemangiosarcoma (HHS). In contrast to the treatment algorithms for hepatocellular and cholangiocellular cancer, the diagnostic and therapeutic approaches to HEHE and HHS are not well developed. The related uncertainty is explained by their rare occurrence and their protean clinical, morphological (imaging) and histopathological presentation and behaviour. This article gives an update about these particular tumours based on the analysis of the recent literature and of the studies on vascular tumours published by the European Liver Intestine Transplantation Association (ELITA)-European Liver Transplant Registry (ELTR). It focuses also on the place of liver transplantation (LT) in the respective therapeutic algorithms. The differential diagnosis between these vascular and other tumour types may be very difficult. Correct diagnosis is of utmost importance and is based on a high index of clinical suspicion and on the integration of clinical, radiological, histological [including immunohistochemistry (IHC) and molecular biology findings]. Surgery, be it partial or total hepatectomy (LT), should be proposed whenever possible, because it is the therapeutic mainstay. In HEHE, LT provides excellent results, with long-term disease-free survivals (DFS) reaching 75%. Good results can be obtained even in case of (frequent) extrahepatic spread. Based on the extensive ELITA-ELTR study a HEHE-LT prognostic score has been proposed in order to estimate the risk of recurrence after LT. In contrast, results of surgery and LT are extremely poor for HHS, for the almost invariably rapid recurrence (within 6 months) and related death within 2 years. LT remains a contraindication for HHS. Due to the still important recurrence rate after surgical resection (25% in HEHE and almost 100% in HHS), there is an urgent need to develop pharmacological treatments targeting angiogenic and non-VEGF angiogenic pathways. To date, some prospective pilot studies and case reports have shown some short-term stabilisation of the disease in small groups of patients. In order to make progress, combination of surgery, anti-angiogenic and immunotherapy seems worthwhile. To complete the panel of vascular liver tumours, infantile haemangioendothelioma, haemangiopericytoma, nodular regenerative hyperplasia (NRH) and hepatic small vessel neoplasms (HSVN) are also discussed.

Hepatic tumors of vascular origin: imaging appearances

A number of benign and malignant neoplasms may arise from the vascular elements within the liver parenchyma. Lesions discussed in this article include angiosarcoma, epithelioid hemangioendothelioma, solitary fibrous tumor (hemangiopericytoma), infantile, and cavernous hemangiomas. Despite a common theme of vascular origin, the pathologic and imaging appearance of these entities can be heterogeneous. Angiosarcomas are bizarrely enhancing, highly aggressive tumors, which often present with metastatic disease. When solitary, epithelioid hemangioendothelioma lesions can exhibit a concentric ring or target appearance on contrast-enhanced CT and at MR and when numerous may be indistinguishable from angiosarcoma except for a more slowly advancing course. Primary solitary fibrous tumors of the liver are exceedingly rare solid masses and most often initially diagnosed on imaging as other entities such as cholangiocarcinoma. Infantile hemangiomas consist of benign proliferation of the vascular endothelium and in the absence of flow-related complications, are usually clinically silent, and may be detected incidentally as T1 hypointense, T2 hyperintense, centripetally enhancing lesions. Cavernous hemangiomas are extremely common hepatic lesions and when classic rarely offer a challenge in diagnosis, though atypical variants may mimic more serious diseases. The purpose of this review is to provide an overview of important vascular tumors of the liver in order to aid the radiologist in providing a broad differential diagnosis for focal liver lesions, and when classic, suggest specific uncommonly seen diagnoses in order to more accurately guide clinical management.

Solitary Fibrous Tumors in Pediatric Patients: A Rare and Potentially Overdiagnosed Neoplasm, Confirmed by STAT6 Immunohistochemistry

Pathological diagnosis of solitary fibrous tumor (SFT) in the pediatric population is challenging, as it occurs uncommonly in this age-group and resembles other spindle cell neoplasms. SFT contains a NAB2-STAT6 fusion gene, which can be reliably detected using STAT6 immunohistochemistry. Positive staining is highly sensitive and specific. We sought to investigate the utility of STAT6 immunohistochemistry, to show how commonly SFT was historically recognized at 3 academic pediatric institutions, to reclassify them when appropriate, and to demonstrate features of major mimics of SFT. Our series included cases with a previous diagnosis of SFT or for which SFT was among key considerations, from 3 major academic pediatric hospitals seen over the past 30 years. Of 18 tumors identified, only 3 tumors from 2 patients demonstrated positive STAT6 staining as well as the typical histology and immunophenotype seen in SFT. The remaining 15 tumors were reclassified based on morphology, additional immunohistochemistry and fluorescence in situ hybridization as desmoid-type fibromatosis (3 tumors), nerve sheath/neural tumors (3 tumors), low-grade fibromyxoid sarcoma, medallion-like dermal fibroma, poorly differentiated Sertoli cell tumor, nodular/proliferative fasciitis, calcifying fibrous tumor, aneurysmal bone cyst of soft tissue, STAT6-negative SFT with adipocytic differentiation, undifferentiated small round blue cell tumor, and scar (1 tumor each). Our study confirms that SFT is rare in the pediatric population and that it is potentially overdiagnosed. STAT6 immunohistochemistry is recommended to confirm the diagnosis of SFT in the pediatric population.

Unusual occurrence of orbital hemangiopericytoma in the zygomatic bone of an adolescent: a case report

Background

Hemangiopericytoma and solitary fibrous tumor are considered related variants on the same spectrum and both may essentially be the same tumor. They are infrequently encountered in the orbital region while the zygomatic bone is an extremely rare location for these neoplasms to occur.

Case presentation

A 14-year-old boy presented with complaint of deformity of left infraorbital area and a firm, regular mass in the region. Orbital CT scan revealed a well-defined round isodense intraosseous lesion in the lowermost portion of the lateral orbital wall (zygomatic bone), expanding the bone and protruding anteriorly and medially. MRI showed the mass to be heterogenous and strongly enhancing with contrast medium. Inferior transconjunctival orbitotomy was performed and the mass was removed. The histopathologic examination and immunohistochemistry staining results (positive for CD34, CD31 and smooth muscle actin, but negative for CD99, S100, B-cell lymphoma 2 (bcl-2) and desmin) confirmed the diagnosis of hemangiopericytoma. The postoperative course was uneventful, with no evidence of recurrence after 5 years follow up.

Conclusions

This case represents the second hemangiopericytoma reported in the zygomatic bone. Although extremely rare, hemangiopericytoma/solitary fibrous tumor might be considered in the differential diagnosis of intraosseous lesions of the orbital and zygomatic region.

Grading of meningeal solitary fibrous tumors/hemangiopericytomas: analysis of the prognostic value of the Marseille Grading System in a cohort of 132 patients

The finding that meningeal solitary fibrous tumors (SFTs) and meningeal hemangiopericytomas (HPCs) are both characterized by NAB2-STAT6 gene fusion has pushed their inclusion in the WHO 2016 Classification of tumors of the central nervous system (CNS) as different manifestations of the same entity. Given that the clinical behavior of the CNS SFT/HPC spectrum ranges from benign to malignant, it is presently unclear whether the grading criteria are still adequate. Here, we present the results of a study that analyzed the prognostic value of an updated version of the Marseille Grading System (MGS) in a retrospectively assembled cohort of 132 primary meningeal SFTs/HPCs with nuclear overexpression of STAT6. The median patient follow-up was 64 months (range 4-274 months); 73 cases (55%) were MGS I, 50 cases (38%) MGS II and 9 cases (7%) were MGS III. Progression-free survival (PFS) and disease-specific survival (DSS) were investigated using univariate analysis: the prognostic factors for PFS included MGS, extent of surgery, radiotherapy, chemotherapy and mitotic activity ≥5/10 high-power field (HPF). Moreover, MGS, radiotherapy, mitotic activity ≥5/10 HPF, and necrosis were the prognostic factors measured for DSS. In multivariate analysis, extent of surgery, mitotic activity ≥5/10 HPF, MGS I and MGS III were the independent prognostic factors measured for PFS while necrosis, MGS III and radiotherapy were the independent prognostic factors for DSS. In conclusion, our results show that assessing the malignancy risk of SFT/HPC should not rely on one single criterion like mitotic activity. Therefore, MGS is useful as it combines the value of different criteria. In particular, the combination of a high mitotic activity and necrosis (MGS III) indicates a particularly poor prognosis.

Prediction of local and metastatic recurrence in solitary fibrous tumor: construction of a risk calculator in a multicenter cohort from the French Sarcoma Group (FSG) database

Background

Solitary fibrous tumors (SFT) are rare unusual ubiquitous soft tissue tumors that are presumed to be of fibroblastic differentiation. At present, the challenge is to establish accurate prognostic factors.

Patients and methods

A total of 214 consecutive patients with SFT diagnosed in 24 participating cancer centers were entered into the European database (www.conticabase.org) to perform univariate and multivariate analysis for overall survival (OS), local recurrence incidence (LRI) and metastatic recurrence incidence (MRI) by taking competing risks into account. A prognostic model was constructed for LRI and MRI. Internal and external validations of the prognostic models were carried out. An individual risk calculator was carried out to quantify the risk of both local and metastatic recurrence.

Results

We restricted our analysis to 162 patients with local disease. Twenty patients (12.3%) were deceased at the time of analysis and the median OS was not reached. The LRI rates at 10 and 20 years were 19.2% and 38.6%, respectively. The MRI rates at 10 and 20 years were 31.4% and 49.8%, respectively. Multivariate analysis retained age and mitotic count tended to significance for predicting OS. The factors influencing LRI were viscera localization, radiotherapy and age. Mitotic count, tumor localization other than limb and age had independent values for MRI. Three prognostic groups for OS were defined based on the number of unfavorable prognostic factors and calculations were carried out to predict the risk of local and metastatic recurrence for individual patients.

Conclusion

LRI and MRI rates increased between 10 and 20 years so relapses were delayed, suggesting that long-term monitoring is useful. This study also shows that different prognostic SFT sub-groups could benefit from different therapeutic strategies and that use of a survival calculator could become standard practice in SFTs to individualize treatment based on the clinical situation.

Hemangiopericytoma of the Nasal Cavity: A Review of 15 Cases over a 40-Year Period

Hemangiopericytomas are rare tumors of vascular origin most commonly found in the extremities or retroperitoneal area. When they originate from the nasal cavity and paranasal sinuses, they tend to be less aggressive and generally do not metastasize. The term “hemangiopericytoma-like lesion” has been coined for sinonasal hemangiopericytomas that display more benign histologic and growth characteristics than do those located elsewhere. Fifteen cases of hemangiopericytoma of the nasal cavity and paranasal sinuses were reviewed over the period 1951 to 1990; included are follow-up data on cases reported earlier from this institution. The clinical course, management, and outcome was evaluated and correlated with the histologic characteristics of the tumors. The recurrence rate in our series was 13.3%; the mean follow-up was 11 years. No patients died of their disease or had evidence of metastatic disease. This clinicopathologic review suggests that sinonasal hemangiopericytomas should not be classified as “hemangiopericytoma-like” lesions; rather, they should be expected to have significant local recurrence rates with low rates of distant metastasis and mortality. Long-term follow-up is essential as there can be local recurrence after many years.

Nasal Septal Hemangiopericytoma-like Tumor: A Case Report with an Immunohistochemical Study

Nasal hemangiopericytoma-like (HPCL) tumor is a rare vascular tumor and should be differentiated from typical hemangiopericytomas (HPCs). This study reports the case of an HPCL tumor in a 77-year-old man with histological and immunohistochemical features. After preoperative evaluation of the blood supply, the dark-red right intranasal tumor was resected completely via the right maxillary sinus. The final histopathological diagnosis was HPCL tumor based on several stains: vimentin (+), α-SMA (+), etc. Moreover, there were few p53 (+) cells and the Ki-67 and topoisomerase IIα labeling indices were both under 5%. These findings indicated that this tumor was a low-grade malignancy. The immunohistochemical investigations used are useful for making the diagnosis of HPCL tumor and determining the treatment, malignancy, and prognosis. (American Journal of Rhinology 15 267–270, 2001)