Extrapleural solitary fibrous tumor: a clinicopathologic study of 19 cases

CT and MR Imaging of Retroperitoneal Sarcomas: A Practical Guide for the Radiologist

Primary retroperitoneal sarcomas (RPS) represent around 10-16% of all sarcomas, with liposarcomas and leiomyosarcomas being the most common subtypes. RPS have some peculiar characteristics, imaging appearances, worse prognosis, and complications compared to other locations of sarcoma. Commonly, RPS primarily present as large masses, progressively encasing adjacent structures, causing mass effect, and complications. RPS diagnosis is often challenging, and these tumors may be overlooked; however, failure to recognize RPS characteristics leads to a worse prognosis for the patients. Surgery is the only recognized curative treatment, but the anatomical constraints of the retroperitoneum limit the ability to achieve wide resection margins; therefore, these tumors have a high rate of recurrence, and require long-term follow-up. The radiologist has an important role in the diagnosis of RPS, the definition of their extent, and their follow-up. Specific knowledge of the main imaging findings is required to reach an early diagnosis, and, ultimately, to guarantee the best patient management. This article provides an overview of the current knowledge regarding cross-sectional imaging features of patients with retroperitoneal sarcomas, presenting tips and tricks to improve imaging diagnosis of RPS.

Epithelioid and Clear Cell Solitary Fibrous Tumors: Clinicopathologic, Immunohistochemical, and Molecular Genetic Study of 13 Cases

Solitary fibrous tumors (SFTs) are ubiquitous soft tissue neoplasms known for their protean histology and potentially aggressive behavior. Although most cases are composed of a monotonous proliferation of spindle cells, some tumors show unusual cytologic features. We have studied 13 SFTs that were characterized by a predominant population of round epithelioid cells with abundant eosinophilic cytoplasm and clear cell changes. The tumors occurred in 8 women and 5 men, aged 36 to 80 years (mean=63 y), and were located within the orbit (3), lower extremity (3), retroperitoneum (2), abdominal cavity (2), and superficial soft tissues of the neck, pelvis, and pubis (1 each). The tumors measured from 3.5 to 24.5 cm. Using a risk assessment system, 6 cases were stratified as low-risk tumors; 3 of these showed no evidence of recurrence or metastases from 6 to 18 years, and 1 tumor in the orbit recurred and led to the patient's demise. Five cases were of intermediate risk; clinical follow-up showed no evidence of recurrence or metastases from 3 to 4 years in 3 patients, and 1 patient suffered a recurrence 4 years after diagnosis. Two cases were high risk; 1 patient died after 1 year and the second patient experienced local recurrence at 4 years. Immunohistochemical studies showed nuclear positivity for STAT6 in 10 cases. CD34 immunohistochemistry was positive in 11 cases. A NAB2::STAT6 rearrangement was present in all cases. Epithelioid and clear cell SFT should be considered in the differential diagnosis of soft tissue neoplasms with epithelioid and clear cell morphology.

A Large Solitary Fibrous Tumor of the Nasal Cavity and Paranasal Sinuses Involving the Anterior Frontal Fossa: A Case Report and Review of the Literature

The Solitary Fibrous Tumor (SFT) is a rare mesenchymal neoplasm that arises mainly from the pleura. The sinonasal tract is generally not affected by SFT, and less than 100 cases have been reported in the English literature to date. We report an extremely rare SFT of the nasal cavity and paranasal sinuses extending into the anterior frontal fossa through the floor of the anterior skull base. To our knowledge, this case is the fourth SFT of the sinonasal tract involving the anterior frontal fossa in the world. Meanwhile, the tumor, measuring 13 × 6 cm in images, is the largest SFT of the sinonasal tract compared to previously reported cases. Three surgical procedures, including a transcranial one, were performed for the patient to achieve complete removal of the tumor. The diagnosis of SFT was established primarily by immunohistochemical positivity for CD34, STAT6, and negativity for S-100 protein. We emphasize the possibility of recurrence in SFT, and close follow-up is necessary with the help of nasal endoscopy and imaging approaches.

Soft tissue solitary fibrous tumors of the musculoskeletal system: spectrum of MRI appearances and characteristic imaging features

OBJECTIVE

Solitary fibrous tumors (SFTs) uncommonly occur in the musculoskeletal system, with limited available data on their MRI appearance. This study was performed to assess the MRI features of SFTs in the musculoskeletal system (MSK-SFTs).

MATERIALS AND METHODS

Pre-treatment MRI in 39 patients with pathologically proven SFTs in the trunk or extremities was evaluated. Patient demographics, clinical management and follow-up, and lesion histology were reviewed. MRI features including lesion location, size, morphology, signal characteristics, vascularity, and relationship to major neurovascular structures were assessed.

RESULTS

MSK-SFTs most frequently occurred in the lower extremity (23/39 cases, 59%), deep to fascia (29/39, 74%), and intermuscular (22/29, 76%) in location. The majority of deep lesions were located along a major neurovascular bundle (20/29, 69%). Lesions had well-defined margins (39/39, 100%), multilobulated contours (27/39, 69%), and measured mean 6.9 ± 2.8 cm. The majority of lesions had slightly hyperintense T1 signal (34/39, 87%) and heterogenous intermediate-to-high T2/STIR signal (28/38, 74%). A "pseudo-cerebriform" internal architectural pattern on fluid-sensitive sequences, with internal lobulations and low signal bands/septations, was observed in 63% (24/38) of lesions. Lesions commonly demonstrated prominent intra-lesional (30/39, 75%) and peripheral juxta-lesional flow voids. Local invasion of surrounding structures was uncommon (3/39, 8%). Mitotically active lesions (p = 0.02) and lesions with tumor necrosis (p < 0.01) were larger in size. Tumor necrosis was associated with T1 heterogeneity (p = 0.04). Distant metastasis occurred in 10% (4/39) of patients, all in mitotically active lesions pre-operatively considered at least at intermediate risk of metastasis.

CONCLUSION

MSK-SFTs commonly present as well-defined, hypervascular masses deep to fascia along major neurovascular bundles, with heterogeneous slightly hyperintense T1 signal, intermediate-to-high T2/STIR signal, and prominent macroscopic flow voids.

Radiologic-Pathologic Correlation of Primary Retroperitoneal Neoplasms

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

Solitary Fibrous Tumors of the Chest: An Analysis of Fifty Patients

Background

A solitary fibrous tumor of the chest (SFTC) is a subtype of solitary fibrous tumor (SFT) with a low incidence rate. The purpose of this study is to analyze the diagnosis and treatment of SFTC and the difference between benign and malignant solitary fibrous tumor of the pleura (SFTP) to improve the understanding of this rare disease.

Methods

A retrospective analysis of fifty patients with SFTC (33 cases in the pleura and 17 in the lung) was performed. Clinical and imaging characteristics, pathological features, and treatment follow-up outcomes were analyzed.

Results

The common symptoms of the 50 patients included a cough, expectoration, chest tightness, fever, and chest pain. Space occupying lesions were found via plain computed tomography (CT) and enhanced CT was used for enhancement of the tumors. It was also found that 18 cases had necrosis, and 5 cases had calcification. The histopathology results showed that frequent nuclear division, obvious morphological variation, necrosis, and the high expression of Ki-67 cells are markers of malignant SFTC. There were significant differences in age, chest tightness, necrotic foci in CT, and expression of Ki-67 between the benign and malignant SFTP cases. All the patients who received treatment were given an excellent prognosis.

Conclusion

A combination of enhanced CT, histopathology, and immunohistochemistry can be used for the accurate diagnosis of SFTC. Advanced age, chest tightness, necrotic foci in CT, and a high Ki-67 index were more likely to be malignant SFTP. Operation and radiofrequency ablation can provide favorable outcomes for both benign and malignant SFTC.

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.

Dumbbell-shaped solitary fibrous tumor in the parapharyngeal space: A case report

BACKGROUND

Solitary fibrous tumors (SFTs) occurring in the parapharyngeal space are rare, and their final diagnosis depends on pathological and immunohistochemical analyses. Once the tumor is diagnosed, complete resection and regular postoperative follow-up are required.

CASE SUMMARY

A 40-year-old male patient with a right parotid gland mass discovered 8 years ago was admitted to hospital. The mass showed no tenderness or local skin redness. Imaging was carried out as the patient had stable vital signs and showed that the mass was a dumbbell-shaped tumor comprising a superficial tumor approximately 5 cm long and 3 cm wide in size that compressed the right parotid gland and a deep tumor located in the right parapharyngeal space approximately 4.5 cm long and 2.5 cm wide in size. Both tumors were connected in the middle. Prior to surgery, the tumors were considered to be parapharyngeal schwannomas. During surgical dissection, the tumors were found to be smooth and tough, without obvious adhesion to the surrounding tissues. The tumors were revealed to be a SFT following postoperative pathological analysis.

CONCLUSION

SFTs in the parapharyngeal space are rarely reported, and complete resection of such tumor is recommended. Adjuvant chemoradiotherapy is used in patients with extensive tumor invasion to lower the recurrence rate. Postoperative long-term follow-up is required.

Sinonasal haemangiopericytoma- An unusual swelling in the nasal cavity

Sinonasal hemangiopericytoma, also known as glomangiopericytoma (GPC) is a benign perivascular tumor of low malignant potential, with an incidence rate of 0.5-1% of all sinonasal tumors. It often shows local recurrences with invasion to the surrounding bony tissues. It usually arises from the perivascular cells surrounding the capillaries. Etiology of the tumour is uncertain, with few postulated hypothesis like pregnancy, trauma, hypertension and corticosteroid drugs. They have an indolent course and tend to occur most commonly in the adults of seventh decade of life. We present a case report of 55 years old male presenting to the ENT OPD, with complaints of right sided nasal obstruction and repeated episodes of epistaxis since the last 9 months. History and general examination was unremarkable except for anti-hypertensive intake since the last few years. Laboratory investigations showed microcytic hypochromic anaemia, raised absolute eosinophil count of 1500 cells per microliter and positive Hepatitis B surface antigen (HBsAg) in the blood. Rhinoscopic examination showed a reddish brown nodular swelling in the right nasal cavity beneath the middle turbinate and hypertrophy of left nasal mucosa. CT imaging suggested an 18x15 mms, well defined soft tissue mass in the right nasal cavity. Complete resection of the mass with endoscopic surgery was performed. Histopathological examination coupled with immunohistochemistry confirmed the diagnosis of Sinonasal Hemangiopericytoma. This case report stresses upon various differential diagnosis of sinonasal swellings and the importance of considering long term follow up of Sinonasal Hemagiopericytoma.

Outcome of patients with primary retroperitoneal solitary fibrous sarcoma

BACKGROUND

To describe the clinicopathological features of primary retroperitoneal solitary fibrous tumor (RSFT) and define the prognostic factors.

METHODS

The comprehensive data of 35 primary RSFT patients who got curative surgery at a tertiary cancer center from April 2004 to October 2018 were retrospectively analyzed.

RESULTS

Male patients outnumbered female patients (19 vs. 16), with the age ranging from 19 to 73 years (median, 51 years). 7 (20%) patients had tumors located in special parts, including three in kidney, one in renal pelvis, one in bladder, one in prostate, and one in mesentery. Tumor sizes ranged from 2.5 to 25 cm (median, 9 cm). Microscopic negative margin was reached in 33 (94.3%) cases. 13 (37.1%) were classified as atypical/malignant, while 22 (62.9%) were benign. Concomitant organ excision was performed on 11 (31.4%) patients, with kidney (n = 5) being the most frequent organ. Multifocality was only found in 4 (11.4%) cases. The majority of the patients (31, 88.6%) did not get adjuvant treatment. The median follow-up time was 46 months (range 4-153 months). The 5-year DSS rate and DFS rate were 100% and 63.6%, respectively. In univariate analysis, tumor size ≥ 10 cm (P = 0.002) and atypical/malignant pathology (P = 0.024) were associated with decreased DFS. Multivariate analysis revealed that tumor size was the only independent prognostic factor for DFS (HR 6.03, 95% CI 1.18-30.77, P = 0.031).

CONCLUSION

RSFT is uncommon, slow-growing, and recrudescent tumors. Large tumor size and malignant pathology are associated with decreased DFS. Tumor size ≥ 10 cm independently predicts shortened DFS.

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.

Extremely rare case of intravascular solitary fibrous tumour in the inferior vena cava with review of the literature

BACKGROUND

Solitary fibrous tumour (SFT) is a mesenchymal tumour of fibroblastic type, and it develops in almost any part of the human body. However, according to previous studies, the occurrence of intravascular SFTs is extremely rare.

CASE PRESENTATION

We reported a case of intravascular SFT in a 67-year-old woman who has been experiencing swelling and pain in the right leg for 2 months. Computed tomography venography scan revealed a well-defined mass obstructing the inferior vena cava (IVC). Surgical resection was performed, and histopathologic and immunohistochemical results were consistent with SFT. Further, next-generation sequencing (NGS) analysis was performed, and results revealed two tumour-related gene mutations (deletion of PMS2 and variation of ESR1 [L536P]). The patient did not receive any adjuvant therapy, and no signs of tumour progression were observed during the 6-month follow-up.

CONCLUSION

To the best of our knowledge, this study first presented about SFT arising from the IVC and carried out an NGS analysis to validate the molecular mechanism of such condition.

Clinical and pathological analysis of solitary fibrous tumors with portal vein widening: A case report

RATIONALE

Solitary fibrous tumors (SFTs) are rare soft-tissue tumors characterized with spindle-cell, which occur more common in the chest and rarely seen in the abdomen. So far as we knew, SFTs accompanied with venopathy of portal vein has rarely been reported.

PATIENT CONCERNS

A 36-year-old male presented with left-sided abdominal mass and portal vein expansion on ultrasound.

DIAGNOSES

The post-operative histopathology confirmed the diagnosis of Solitary fibrous tumor.

INTERVENTIONS

Laparotomy was performed and the mass was completely removed.

OUTCOMES

Patients had no symptoms, recovered well without recurrence; the portal vein and splenic vein dilatation were alleviated and the symptoms of portal hypertension were relieved.

LESSONS

SFTs presents with few symptoms in the early stage of the disease. A rich arteriovenous shunt is beneficial to the diagnosis of SFTs by B-ultrasound and computed tomography (CT) examinations. However, the diagnosis of SFTs must depend on histopathology.

Surgical treatment of primary solitary fibrous tumors involving the pelvic ring

The surgical treatment of primary solitary fibrous tumors (SFT) involving the pelvic ring has not been reported previously. In this study, we aimed to evaluate the efficacy of surgical treatment for this disease. From 2009 to 2015, 13 patients underwent tumor resection at our hospital, with an average age of 49.5 years (27–68 years). Four patients underwent en bloc resection, and 9 patients underwent piecemeal resections. A Chi-square test was used to compare the postoperative recurrence rates between the en bloc resection and the piecemeal resection groups (p = 0.68), and no significant difference was found between the benign and malignant solitary fibrous tumor groups (p = 0.44). The 5-year survival rate of the patients in this study was 83.3%, and the 5-year progression-free survival rate was 63.5%. The progression-free survival rate was not significantly different between the en bloc resection and piecemeal resection groups (p = 0.97). Piecemeal resection can also achieve acceptable local control, particularly for patients with sacral tumors, as they may achieve even better postoperative function with sacral nerve preservation. Recurrence and metastasis occur relatively late in the course of this disease. Therefore, long-term follow-up is required.

Late Onset of Non-islet Cell Tumor Hypoglycemia Managed via Multidisciplinary Treatment in a Patient with a Solitary Fibrous Tumor

Solitary fibrous tumor (SFT) is a rare subtype of soft tissue sarcoma (STS). We herein describe a case of late onset of non-islet cell tumor hypoglycemia (NICTH) that was managed via multidisciplinary treatment in a patient with SFT. A 67-year-old man previously diagnosed with SFT 4 years prior to this presentation and treated with several rounds of surgery, presented with massive tumors. Eighteen months following his prescribed chemotherapy, the patient developed hypoglycemia. He was diagnosed with NICTH, after confirming the presence of high molecular weight insulin-like growth factor-2. This case suggests that paraneoplastic syndrome can occur even in cases of rare cancers, such as STS.

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.

Extrapleural solitary fibrous tumor: A distinct entity from pleural solitary fibrous tumor. An update on clinical, molecular and diagnostic features

Solitary fibrous tumor (SFT) is a mesenchymal neoplasm that was originally described to be localized in the pleura, but thereafter, this has been reported in several anatomic sites. Although the etiology of the neoplasm remains largely unknown, the pathogenesis seems to be related to an NAB2-STAT6 fusion gene due to paracentric inversion on chromosome 12q13. The diagnosis of extrapleural SFT is challenging, owing to its rarity, and requires an integrated approach that includes specific clinical, histological, immunohistochemical, and even molecular findings. Histologically, extrapleural SFT shares morphological features same as those of the pleural SFT because it is characterized by a patternless distribution of both oval- and spindle-shaped cells in a variable collagen stroma. In addition, morphological variants of mixoid, fat-forming, and giant cell-rich tumors are described. A correct diagnosis is mandatory for a proper therapy and management of the patients with extrapleural SFT, as extrapleural SFT is usually more aggressive than pleural form, particularly cases occurring in the mediastinum, retroperitoneum, pelvis, and meninges. Although SFT is usually considered as a clinically indolent neoplasm, the prognosis is substantially unpredictable and only partially related to morphological features. In this context, cellularity, neoplastic borders, cellular atypias, and mitotic activity can show a wide range of variability. We review extrapleural SFT by discussing diagnostic clues, differential diagnosis, recent molecular findings, and prognostic factors.

Solitary fibrous tumor/hemangiopericytoma: treatment results based on the 2016 WHO classification

OBJECTIVE

Solitary fibrous tumor/hemangiopericytoma (SFT/HPC) is a new combined entity for which a soft-tissue-type grading system, ranging from grades I to III, has been introduced in the 2016 WHO classification of tumors of the CNS. The results of the treatment of this new disease entity require evaluation.

METHODS

The authors retrospectively reevaluated the pathological findings and medical records of patients with SFT/HPC. This study included 60 patients (27 men and 33 women, median age 42.5 years, range 13-69 years) treated at Severance Hospital between February 1981 and February 2016. Four, 40, and 16 patients were categorized as having SFT/HPC grades I, II, and III, respectively. Among these patients, SFTs diagnosed in 7 patients were regraded as grades I (n = 4), II (n = 2), and III (n = 1).

RESULTS

The median overall survival (OS) was 73.2 months (range 1.4-275.7 months), and the progression-free survival (PFS) after the first operation was 53.8 months (range 1.4-217.7 months). Six patients (10%) showed extracranial metastasis during a median period of 103.7 months (range 31.9-182.3 months). Nineteen patients (31.7%) presented with tumor recurrences. The patients in the grade III group had shorter PFS and OS, as well as a shorter period to extracranial metastasis, compared with patients in the grade II group. In the grade II group, patients who underwent gross-total resection showed longer PFS than those who underwent subtotal resection; however, there was no difference in OS. Patients who underwent adjuvant radiation therapy (RT) after surgery had longer PFS compared with that of patients who did not undergo adjuvant RT.

CONCLUSIONS

The SFT/HPC grade I group showed a relatively benign course compared with those of the other groups. The grade III group presented a course with a more aggressive nature than that of the grade II group. In the grade II group, the extent of resection and adjuvant RT was significantly associated with longer PFS. The long-term follow-up and periodic systemic evaluation are mandatory to detect systemic metastasis.

Sinonasal Tract Solitary Fibrous Tumor: A Clinicopathologic Study of Six Cases with a Comprehensive Review of the Literature

Solitary fibrous tumors (SFTs) are well recognized in the head and neck region, but rarely arise in the sinonasal tract (SNT). Six primary SNT SFTs were identified in the files of Southern California Permanente Medical Group between 2006 and 2017. The patients included five males and one female ranging in age from 33 to 72 years (mean 52 years), most of whom presented clinically with nasal obstruction. Three tumors involved the nasal cavity alone, one involved the paranasal sinuses, and two involved both the nasal cavity and paranasal sinuses. Histologically, the tumors were characterized by a variably cellular proliferation of cytologically bland spindle cells within a collagenous stroma with prominent interspersed branching vessels. Mitotic activity was low (range 0-2 per 10 high power fields) and there was no evidence of pleomorphism or tumor necrosis. Surface ulceration was noted. By immunohistochemistry, the lesional cells were positive for CD34, STAT6 and bcl-2. Clinical follow up information was available for all patients (range 32-102 months; mean 72 months). There were no recurrences or metastases and all were alive with no evidence of disease at last follow-up. SFTs rarely affect the SNT, but should be considered in the differential diagnosis of SNT mesenchymal lesions. Immunohistochemical expression of STAT6 can aid in diagnosis and separation of SFT from other spindle cell lesions occurring at this anatomic site. In combination with cases reported in the literature, primary SNT SFT behave in an indolent manner with conservative treatment.

Size and Location are the Most Important Risk Factors for Malignant Behavior in Resected Solitary Fibrous Tumors

PURPOSE

While previously thought to be clinically indolent, recent data suggest significant late metastatic capacity of solitary fibrous tumors (SFTs). We define prognostic factors for recurrence and disease-specific death (DSD) in resected primary SFTs.

METHODS

Resected primary SFTs from 1982 to 2015 were identified from a prospective, single institutional database. Risk factors for local (LR) and distant recurrence (DR), and DSD were assessed using competing risk analysis.

RESULTS

A total of 219 patients with median follow-up of 6.1 (0.1-22) years were included. Five- and 10-year cumulative DSD was 9 and 11%, respectively. Size greater than the median 8 cm, gender, location, and complete gross resection were significantly associated with DSD (p < 0.05). Five- and 10-year cumulative risk (CR) of LR was 4 and 7%, whereas 5- and 10-year CR of DR was 13 and 16%, respectively. LR was associated with location (p = 0.02) and tumor size (p = 0.02), and DR was associated with size (p < 0.01). Histopathologic classification did not predict long-term behavior with both malignant and benign tumors demonstrating capacity for DR and associated death. Tumors in the thoracic cavity and abdomen/retroperitoneum presented the greatest risk of DR (16 and 27% 10-year CR). On multivariate analysis, size ≥ 8 cm (hazard ratio 2.89, p = 0.05) and tumor location in chest or abdominal/retroperitoneal cavity (hazard ratio 2.68, p = 0.01) significantly impacted DSD.

CONCLUSIONS

Recurrence is highly associated with DSD and events occur as late as 16 years after initial presentation, including in patients with initially considered benign tumors. Patients with large (≥ 8 cm) tumors in the chest or abdominal/retroperitoneal cavity are at greatest risk.

Sinonasal and rhinopharyngeal solitary fibrous tumour: a case report and review of the literature

Solitary fibrous tumours are rare neoplasms that arise mostly from the pleura. Much more rarely they can also be found in extrapleural sites, including the head and neck. We report a rare case of a sinonasal and rhinopharyngeal solitary fibrous tumour. The tumour, measuring 67 x 28 x 55 mm, was first embolised and then successfully removed through endonasal endoscopic surgery. Histopathologic analysis confirmed the nature of the lesion, which was positive for CD34 and vimentin. A post-operative CT scan and endoscopic follow-up demonstrated total resection and absence of recurrence after 13 months.

Extrapleural solitary fibrous tumor in thymic area: A case report

RATIONALE

Solitary fibrous tumor (SFT) is a rare benign soft tissue mesenchymal neoplasm. There have been a few reports of extrapleural SFTs although it can occur anywhere in the body.

PATIENT CONCERNS

A 30-year-old male presented with an anterior neck mass since one month.

DIAGNOSES

Based on physical and radiologic examination, preliminary differential diagnosis was thymic neoplasm or intrathoracic goiter.

INTERVENTIONS

We performed surgical excision of the neck mass.

OUTCOMES

The histopathological examination revealed an extrapleural SFT LESSONS:: We present a case of extrapleural SFT in the thymus which was misdiagnosed as thymoma based on radiologic findings.

The NAB2-STAT6 gene fusion in solitary fibrous tumor can be reliably detected by anchored multiplexed PCR for targeted next-generation sequencing

Solitary fibrous tumor (SFT) is a mesenchymal tumor of fibroblastic origin, which can affect any region of the body. 10-15% of SFTs metastasize and metastatic tumors are uniformly lethal with no effective therapies. The behavior of SFT is difficult to predict based on morphology. Recently, an intrachromosomal gene fusion between NAB2 and STAT6 was identified as the defining driving genetic event of SFT and different fusion types correlated with tumor histology and behavior. Due to the proximity of NAB2 and STAT6 on chromosome 12, this fusion may be missed by fluorescence in-situ hybridization. We evaluated 12 SFTs from 10 patients. All tumors showed strong nuclear staining for STAT6 by immunohistochemistry (IHC). The same formalin-fixed, paraffin-embedded blocks for IHC were used for gene fusion detection by a next-generation sequencing (NGS)-based assay. Targeted RNA fusion sequencing for gene fusions was performed using the Universal RNA Fusion Detection Kit, the Archer(™) FusionPlex(™) Sarcoma Panel and the Ion Torrent PGM, and data were analyzed using the Archer Analysis Pipeline 3.3. All tumors were positive for NAB2-STAT6 fusion. Six types of fusions were detected: NAB2ex4-STAT6ex2, NAB2ex2-STAT6ex5, NAB2ex6-STAT6ex16, NAB2ex6-STAT6ex17, NAB2ex3-STAT6ex18 and NAB2intron6-STAT6Ex17. The NGS findings were confirmed by RT-PCR followed by Sanger sequencing. No STAT6 fusion was detected in selected morphologic mimics of SFT. The assay also allows for detection of novel fusions and can detect NAB2-STAT6 fusions at a single-base resolution.

Resectable extra-pleural and extra-meningeal solitary fibrous tumours: A multi-centre prognostic study

BACKGROUND

Extra-pleural and extra-meningeal solitary fibrous tumour (SFT) is a rare sarcoma histotype curable with surgery in the majority of patients. The behaviour of these tumours ranges from indolent/very low grade to malignant/high grade but it is still not possible to accurately predict prognosis after surgery. We have investigated a multi-centre series to stratify the risk of recurrence to patients with SFTs.

METHODS

We retrospectively analysed the data from 243 patients who underwent surgery (2002-2011) at four sarcoma referral centres.

RESULTS

Upon univariate analysis, hypercellularity, atypia, necrosis, high mitotic rate (ie >4 mitoses/10 HPF) were associated with both disease-free and overall survival. Surgical margins were a significant prognostic factor for disease-free (P = 0.007) but not for overall survival. Unexpectedly, larger tumour size was associated with a better prognosis (P = 0.038) and fewer recurrences (P = 0.024). Upon multivariable analysis, high mitotic rate (hazard ratio, HR = 2.85, P = 0.002), cellular atypia (HR = 1.62, P = 0.015) and hypercellularity (HR = 1.82, P = 0.031) were significantly associated with recurrences. A SFT recurrence score has been provided to stratify risk of recurrence.

CONCLUSION

This study provides a prognostic model to stratify risk of recurrence in patients with resectable SFTs. This allows clinician to decide on an optimal follow-up strategy and to select patients that may benefit from adjuvant treatments.

Malignant Solitary Fibrous Tumor of the Pancreas

Solitary fibrous tumor (SFT) arising in the pancreas is exceedingly rare, with only 11 cases reported in the English literature. All cases described thus far have exhibited benign histology. We report the first case of malignant SFT of the pancreas. The patient was a 52-year-old woman who presented with obstructive jaundice and a 15-cm pancreatic head mass. The mass showed areas with typical histologic features for SFT including small fibroblastlike cells arranged in the well-characterized "patternless pattern" of architecture, hemangiopericytomalike vessels, areas with dense collagen and infrequent mitoses (0-2 per 10 high-power fields [HPFs]). In addition, multiple areas with an overtly sarcomatous morphology were present, containing large spindle and epithelioid cells with nuclear pleomorphism, marked cellularity, up to17 mitoses per 10 HPFs, and necrosis. Immunohistochemical stains were positive for CD34 and B-cell CLL/lymphoma 2 (Bcl-2) in both benign and malignant components and showed strong, diffuse p53 and p16 staining in the malignant component. At last follow-up (40 months), the patient was alive and well without evidence of disease. However, given that the presence of a malignant component in extrapancreatic SFT has been associated with recurrence/metastasis and death, complete surgical resection and close long-term follow-up is required.

Immunosuppression and Multiple Primary Malignancies in Kidney-Transplanted Patients: A Single-Institute Study

Immunodeficiency is associated with higher cancer incidence. However, it is unknown whether there is a link between immunodeficiency and development of multiple primary malignancies. In the present study we analyse this link focusing on kidney-transplanted patients, as they are at higher risk of developing cancer due to the chronic assumption of immunosuppressants. We followed up 1200 patients who underwent kidney transplantation between 1980 and 2012. A total of 77/1200 kidney-transplanted patients developed cancer and 24 of them developed multiple cancers. Most multiple cancers were synchronous with a nonsignificant association between cancer and rejection episodes. In the general cancer population, one-ninth of patients are at higher risk of developing a second tumor over a lifetime; hence it would be reasonable to conclude that, from a merely theoretical and statistical viewpoint, long-term transplanted patients potentially have a higher risk of developing MPMs. However, data did not confirm this assumption, probably because these patients die before a second primary malignancy appears. Despite many observations on the increased incidence of different tumor types in immunodeficient patients and despite immunosuppression certainly being a predisposing factor for the multicancer syndrome, data so far are not robust enough to justify a correlation between immunodeficiency and multiple primary malignancies in transplanted patients.

Prognosis of solitary fibrous tumors: a multicenter study

BACKGROUND

Solitary fibrous tumors (SFTs) are rare mesenchymal tumors, and data regarding outcome and prognostic factors are scarce. We report the outcome and analysis of prognostic factors of a retrospective multicenter cohort study for patients treated for SFTs.

METHODS

Retrospective analysis was performed of patients treated for SFTs between 1995 and 2012. Clinical and histopathological features were analyzed for prognostic value. Endpoints were set at local recurrence, metastasis formation, or death. Survival was analyzed using Kaplan-Meier and Cox proportional hazards analyses.

RESULTS

A total of 81 patients underwent surgical resection of a SFT with curative intent. During follow-up, 21 patients developed distant metastases, while 18 patients developed local recurrence. The 5-year overall survival was 84 %. The local recurrence rate and the metastasis rate at 5 years were 29 and 34 %, respectively. Of all factors analyzed, positive resection margin significantly correlated with local recurrence [hazard ratio (HR) 4.8; 95 % confidence interval (95 % CI) 1.5-14.9]. Tumor size >10 cm (HR 4.4; 95 % CI 1.7-11.5) and high mitosis rate (HR 3.3; 95 % CI 1.06-10.3) significantly correlated with higher incidence of metastases. The combination of tumors >10 cm and high mitosis rate significantly correlated with higher incidence of metastases (HR 4.8; 95 % CI 1.4-16.2) and showed a trend toward worse overall survival (HR 5.7; 95 % CI 0.95-34.7).

CONCLUSIONS

A substantial portion of patients with a SFT developed local recurrence or metastases. Local recurrence is significantly higher in patients with positive resection margins; metastasis frequency is significantly higher in patients with tumors >10 cm and tumors with a high mitosis rate.

Extrathoracic location and "borderline" histology are associated with recurrence of solitary fibrous tumors after surgical resection

BACKGROUND

Most solitary fibrous tumors (SFTs) are cured by complete resection, but many recurrent and metastatic SFTs do not respond to treatment and are fatal. Malignant histology, defined by England's pathologic criteria, is strongly associated with recurrence, but some benign SFTs still behave aggressively. Several studies have suggested that extrathoracic SFTs have a worse prognosis. We reviewed thoracic and extrathoracic SFTs from our institution to determine if extrathoracic location is associated with recurrence, independent of malignant histology.

METHODS

With IRB approval, we retrieved patient pathology reports from the Johns Hopkins Surgical Pathology database between 1991 and 2011 and included 83 SFT patients in our analysis. Patient history and outcomes were obtained from the medical record and primary care physicians. Predictors of recurrence were analyzed by univariate and multivariate analysis and survival determined by the Kaplan-Meier method.

RESULTS

Of the 83 patients, 59 had extrathoracic SFTs in neurologic (n = 24), extremity or head/neck (n = 13), or visceral/intraabdominal (n = 22) sites. A total of 74 SFTs were classified benign and 9 as malignant. Of the 14 recurrences, 13 occurred in extrathoracic SFTs; only 7 were classified as malignant. Multivariate analysis confirmed that malignant histology had the strongest association with recurrence, but extrathoracic location also independently predicted recurrence. A total of 20 benign SFTs possessed 1 or more of England's criteria but to an insufficient degree for malignant classification. These "borderline" SFTs were more likely to recur than benign SFTs without these features.

CONCLUSIONS

Extrathoracic and "borderline" SFTs with any of England's criteria have a higher risk of recurrence.

Pediatric Renal Solitary Fibrous Tumor

Solitary fibrous tumors (SFTs) are unusual spindle cell neoplasms initially described in the pleura but have since been discovered in many extrapleural locations. SFT of the kidney is extremely rare, the majority occurring in middle-aged adults. To date, only two pediatric cases of renal SFT have been reported. We report a case of large SFT in the kidney of a 3-year-old boy that was clinically and radiologically thought to be a nephroblastoma. This case is the first pediatric renal SFT to be reported with detailed histopathologic and cytogenetic analyses. SFT should be included in the differential diagnosis of pediatric renal tumors.

Meningeal hemangiopericytoma and solitary fibrous tumors carry the NAB2-STAT6 fusion and can be diagnosed by nuclear expression of STAT6 protein

Non-central nervous system hemangiopericytoma (HPC) and solitary fibrous tumor (SFT) are considered by pathologists as two variants of a single tumor entity now subsumed under the entity SFT. Recent detection of frequent NAB2-STAT6 fusions in both, HPC and SFT, provided additional support for this view. On the other hand, current neuropathological practice still distinguishes between HPC and SFT. The present study set out to identify genes involved in the formation of meningeal HPC. We performed exome sequencing and detected the NAB2-STAT6 fusion in DNA of 8/10 meningeal HPC thereby providing evidence of close relationship of these tumors with peripheral SFT. Due to the considerable effort required for exome sequencing, we sought to explore surrogate markers for the NAB2-STAT6 fusion protein. We adopted the Duolink proximity ligation assay and demonstrated the presence of NAB2-STAT6 fusion protein in 17/17 HPC and the absence in 15/15 meningiomas. More practical, presence of the NAB2-STAT6 fusion protein resulted in a strong nuclear signal in STAT6 immunohistochemistry. The nuclear reallocation of STAT6 was detected in 35/37 meningeal HPC and 25/25 meningeal SFT but not in 87 meningiomas representing the most important differential diagnosis. Tissues not harboring the NAB2-STAT6 fusion protein presented with nuclear expression of NAB2 and cytoplasmic expression of STAT6 proteins. In conclusion, we provide strong evidence for meningeal HPC and SFT to constitute variants of a single entity which is defined by NAB2-STAT6 fusion. In addition, we demonstrate that this fusion can be rapidly detected by STAT6 immunohistochemistry which shows a consistent nuclear reallocation. This immunohistochemical assay may prove valuable for the differentiation of HPC and SFT from other mesenchymal neoplasms.

Uncommon primary pelvic retroperitoneal masses in adults: a pattern-based imaging approach

There is a broad spectrum of primary pelvic retroperitoneal masses in adults that demonstrate characteristic epidemiologic and histopathologic features and natural histories. These masses may be classified into five distinct subgroups using a pattern-based approach that takes anatomic distribution and certain imaging characteristics into account, allowing greater accuracy in their detection and characterization and helping to optimize patient management. The five groups are cystic (serous and mucinous epithelial neoplasms, pelvic lymphangioma, tailgut cyst, ancient schwannoma), vascular or hypervascular (solitary fibrous tumor, paraganglioma, pelvic arteriovenous malformation, Klippel-Trénaunay-Weber syndrome, extraintestinal GIST [gastrointestinal stromal tumor]), fat-containing (lipoma, liposarcoma, myelolipoma, presacral teratoma), calcified (calcified lymphocele, calcified rejected transplant kidney, rare sarcomas), and myxoid (schwannoma, plexiform neurofibroma, myxoma).Cross-sectional imaging modalities help differentiate the more common gynecologic neoplasms from more unusual masses. In particular, the tissue-specific multiplanar capability of high-resolution magnetic resonance imaging permits better tumor localization and internal characterization, thereby serving as a road map for surgery.

Solitary fibrous tumor: a clinicopathological study of 110 cases and proposed risk assessment model

Solitary fibrous tumor represents a spectrum of mesenchymal tumors, encompassing tumors previously termed hemangiopericytoma, which are classified as having intermediate biological potential (rarely metastasizing) in the 2002 World Health Organization classification scheme. Few series have reported on clinicopathological predictors with outcome data and formal statistical analysis in a large series of primary tumors as a single unified entity. Institutional pathology records were reviewed to identify primary solitary fibrous tumor cases, and histological sections and clinical records reviewed for canonical prognostic indicators, including patient age, tumor size, mitotic index, tumor cellularity, nuclear pleomorphism, and tumor necrosis. Patients (n=103) with resected primary solitary fibrous tumor were identified (excluding meningeal tumors). The most common sites of occurrence were abdomen and pleura; these tumors were larger than those occurring in the extremities, head and neck or trunk, but did not demonstrate significant outcome differences. Overall 5- and 10-year metastasis-free rates were 74 and 55%, respectively, while 5- and 10-year disease-specific survival rates were 89 and 73%. Patient age, tumor size, and mitotic index predicted both time to metastasis and disease-specific mortality, while necrosis predicted metastasis only. A risk stratification model based on age, size, and mitotic index clearly delineated patients at high risk for poor outcomes. While small tumors with low mitotic rates are highly unlikely to metastasize, large tumors ≥ 15 cm, which occur in patients ≥ 55 years, with mitotic figures ≥ 4/10 high-power fields require close follow-up and have a high risk of both metastasis and death.

Solitary fibrous tumor: an update on the spectrum of extrapleural manifestations

Solitary fibrous tumor (SFT) is a rare tumor initially believed to be a benign localized pleural tumor of mesothelial origin. Over the past few years, the literature on this tumor has grown tremendously. The tumor is now reported in diverse bodily locations, and recognized to have a wider range of clinical and radiological features. The most common extrapleural sites of the tumor are the orbits and the extremities. Tumors are often well-circumscribed masses, and vary in size from 1 cm to over 30 cm. The admixture of histological components in the tumor, namely, fibrous tissue, cellular components, and highly vascularized areas consisting of numerous closely packed small to medium-sized blood vessels, influence the imaging appearances of the tumor. On magnetic resonance imaging (MRI), the diagnosis of solitary fibrous tumor is suggested by a well-circumscribed mass that has smooth margins, and focal or diffuse hypointense signal on T2-weighted imaging due to fibrous content in the tumor. SFTs demonstrate strong focal or diffuse contrast enhancement due to the highly vascularized areas in the tumor.

Solitary fibrous tumor of the central nervous system: a 15-year literature survey of 220 cases (August 1996-July 2011)

We reviewed the world literature on solitary fibrous tumors of the central nervous system from August 1996 to July 2011, focusing on both clinicopathological features and diagnostic findings. The anatomical distribution of the 220 cases reported so far reveals that most are intracranial and just over one-fifth are intraspinal. In decreasing frequency, intracranial tumors involve the supratentorial and infratentorial compartments, the pontocerebellar angle, the sellar and parasellar regions, and the cranial nerves. Intraspinal tumors are mainly located in the thoracic and cervical segments. Although most solitary fibrous tumors of the central nervous system are dural based, a small subset presents as subpial, intraparenchymal, intraventricular, or as tumors involving the nerve rootlets with no dural connection. Preoperative imaging and intraoperative findings suggest meningioma, schwannoma or neurofibroma, hemangiopericytoma, or pituitary tumors. Immunohistochemistry is critical to establish a definitive histopathological diagnosis. Vimentin, CD34, BCL2, and CD99 are the most consistently positive markers. The usual histologic type generally behaves in a benign manner if complete removal is achieved. Recurrence is anticipated when resection is subtotal or when the tumor exhibits atypical histology. The proliferative index as assessed by MIB1 labeling is of prognostic significance. Occasionally, tumors featuring conventional morphology may recur, perhaps because of minimal residual disease left behind during surgical extirpation. Rare extracranial metastases and tumor-related deaths are on record. Surgery is the treatment of choice. Stereotactic and external beam radiation therapy may be indicated for postsurgical tumor remnants and for unresectable recurrences. Long-term active surveillance of the patients is mandatory.

The central nervous system solitary fibrous tumor: a review of clinical, imaging and pathologic findings among all reported cases from 1996 to 2010

OBJECTIVE

Central nervous system (CNS) solitary fibrous tumor (SFT) is a rare lesion first identified as a unique entity in 1996. We describe two cases treated at the University of Florida followed by a review of all reported cases of CNS SFT between 1996 and 2010.

METHODS

A review of the literature was performed to identify all reported cases of CNS SFT.

RESULTS

189 cases (including the two presented herein) were discovered, of which 46 were spinal and 143 were intracranial. Demographic, imaging, and pathologic findings are presented. Roughly 6% of reported lesions are malignant. Subtotal resection (STR) was associated with a 16-fold increased odds of recurrence (OR 15.9, 95% CI 5.5-46.1), although mean follow-up was shorter in those cases of GTR without recurrence.

CONCLUSION

CNS SFT is a rare lesion. Six percent of lesions are malignant. GTR is superior to STR although the degree of superiority is not clear.

Sinonasal glomangiopericytoma: case report with emphasis on the differential diagnosis

Glomangiopericytoma (sinonasal-type hemangiopericytoma) is an uncommon sinonasal neoplasm with a perivascular myoid phenotype. This tumor differs from conventional soft tissue hemangiopericytoma in location, biologic behavior, and histologic features. The proposed cell of origin is a modified perivascular glomuslike myoid cell. Glomangiopericytoma is an indolent tumor that tends to arise in the sinonasal tract of older adults and has a low malignant potential with excellent prognosis after surgical resection. Histologically, this lesion is composed of a diffuse, subepithelial proliferation of bland, uniform, closely packed spindled cells growing in a variety of patterns. A distinctive vascular network composed of variably sized vascular channels, the smaller of which demonstrate perivascular hyalinization, is often present. We report the case of a 48-year-old woman with epistaxis and nasal obstruction who was diagnosed with glomangiopericytoma and discuss the histologic differential diagnosis.