Ultrastructural spectrum of solitary fibrous tumor: a unique perivascular tumor with alternative lines of differentiation

Ultrastructural differences between synovial sarcoma and solitary fibrous tumor: comparative study in adult patients from the National Cancer Institute of Mexico

Synovial sarcoma (SS) and solitary fibrous tumor (SFT) are entities with considerable morphological and immunohistochemical similarities that sometimes show a non-confirmatory profile (TLE1 negative, CD34 and focal or negative STAT6 and lack of specific fusion IHC markers), in which the utility ultrastructure is unknown. A cross-sectional, retrospective, analytical, nonexperimental study was carried out by the Department of Pathology of the National Cancer Institute of Mexico (INCan) e from January 1, 2009 to December 31, 2018. With 17 SFT cases with diffuse or focal CD34 and STAT6 positivity and 18 cases of SS with positive FISH molecular test t(X:18) breakapart were studied by electron microscopy of fresh glutaraldehyde fixed or paraffin-embedded tissue. The ultrastructural findings with a significant difference present in the SS were tandem tight junctions, desmosomes and abundance of dilated rough endoplasmic reticulum (RER) cisternae (p < 0.001, 0.003, and 0.001, respectively); while in the (SFT) the presence of abundant glycogen, basal lamina, long and slender cytoplasmic processes, pinocytic vesicles, hemidesmosomes, and/or dense plaques, collagen skein, and microvilli-like buds (p = 0.028, 0.005, and <0.001 for the last five). We then infer that the five distinctive markers of the SFT are the collagen skeins intermingled with cellular processes in a shape of "squid can," and the pinocytic vesicles as they were not observed in any case of SS. Conversely, tandem junctions were not found in any SFT case. Although the presence of multivesicular buds in the SFT was not significant, it had not been previously described.

A Giant Solitary Fibrous Tumour of the Pleura

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

Shapeshifters in Pathology: Paratesticular Solitary Fibrous Tumor Mimicking Leiomyoma

Solitary fibrous tumors are mesenchymal fibroblastic tumors that were originally described as intrathoracic lesions but have since been found to occur in many other locations. They may rarely occur as paratesticular masses. Here we present a peculiar case of a solitary fibrous tumor arising in the paratesticular region and exhibiting leiomyoma-like morphology. Confirmation of the tumor as a solitary fibrous tumor was achieved by RNA sequencing showing NAB2::STAT6 fusion. Possible explanations for the unusual tumor morphology include entrapment of normal smooth muscle elements and tumor differentiation into smooth muscle type cells.

Solitary Fibrous Tumor of the Dorsal Tongue Area

Solitary fibrous tumor (SFT) is a rare tumor occurring in pleura or extrapleural areas. The tongue is infrequently affected, in less than 25 published cases. A female patient, 35 years of age, noticed an oval mass in the posterior dorsal part of the tongue. The operated mass was nodule, 10 mm in size, sharply circumscribed, rather firm. The histology shows uniform CD34 positive spindle tumor cells. The diagnosis of benign SFT of the tongue was made.

Primary solitary fibrous tumor of kidney: A case report and literature review

Primary solitary fibrous tumors of kidney are rare in clinical practice. In literature, only eleven reported cases originated from renal pelvis. We report a case of a 45 year old middle-aged woman who was the first report that a small number of heterosexual cells have been found in urine. Definite diagnosis of this disease still depends on pathological examination, If preoperative puncture or other pathological examination supports the diagnosis of SFTs, the preferred treatment plan for it is surgical resection.

Differentiation between solitary fibrous tumors and schwannomas of the head and neck: an apparent diffusion coefficient histogram analysis

METHODS:

Our study included 5 patients with SFT and 18 patients with schwannoma in the head and neck region for whom pre-operative ADC images were obtained using either 1.5 or 3.0 T MRI system with two b-values. An ADC image that showed the tumor at the largest major diameter was selected for each patient, and a region of interest was set circumscribing the tumor. The histogram distributions of ADC values within the region of interest were compared between SFTs and schwannomas with respect to the mean, standard deviation, median, skewness, kurtosis, and percentile.

RESULTS:

The mean and the median ADC values were significantly higher for schwannomas than in SFTs (p = 0.007 in both). Skewness and kurtosis of ADC histograms were significantly lower for schwannomas than for SFTs (p = 0.002 and 0.005, respectively). ADC values differed greatest between the two tumor groups at the 90th percentile, and were significantly higher for schwannomas than for SFTs (p = 0.005). On receiver operating characteristic curve analysis, the area under the curve for kurtosis, skewness, and the 90th percentile ADC values was 0.92, 0.90, and 0.90, respectively.

CONCLUSIONS:

Our study suggests that skewness on ADC histograms may be the most useful diagnostic factor, followed by kurtosis and the 90th percentile ADC values, for differentiation between SFTs and schwannomas.

Florid Proliferation of Hyalinized Vessels in a Spermatic Cord STAT6 Positive Solitary Fibrous Tumor and Its Potential Clinical Implications

A solitary fibrous tumor (SFT) arising in the paratesticular region is a rare event. Typically most SFTs present as a lung mass and have a characteristic microscopic appearance. Although uncommon, SFTs may present at just about any anatomical site. Here we present a case of a SFT arising along the right spermatic cord, with histologic features mimicking a cellular angiofibroma. We describe the diagnostic immunohistochemical markers useful for arriving at its diagnosis. We also summarize our current understanding of the structural and molecular features that make up SFTs and discuss how these features may help us better understand the pathophysiology of pluripotent mesenchymal stem cell differentiation.

Orbital Hemangiopericytoma in 68Ga-Prostate-Specific Membrane Antigen-HBED-CC PET/CT

A 76-year-old man with biochemical relapse of prostate cancer underwent Ga-prostate-specific membrane antigen PET/CT. Besides a local lymph node metastasis, a nodular structure inside the left orbit caudal to the optic nerve showed increased uptake. A metastasis in this location is unlikely. The subsequently performed MRI showed the structure being T1 hypointense, T2 indifferent, and strongly gadolinium contrast agent enhancing. Histopathologic examination after surgical removal identified the tumor as hemangiopericytoma, which rarely occurs in the orbit. Regarding the intense uptake observed, prostate-specific membrane antigen-targeting PET tracers could bear potential for staging purposes of this tumor entity.

Giant solitary fibrous tumor of the pleura with high-grade sarcomatous overgrowth accompanied by lipid-rich, rhabdomyosarcomatous, and pleomorphic components: A case report

RATIONALE

Solitary fibrous tumors are mesenchymal tumors presenting as fibroblastic neoplasms with prominent branching vascular patterns, which are often generated from the pleura. Most solitary fibrous tumors are benign; however, some can turn malignant. High-grade sarcomas from solitary fibrous tumors include multidirectional histopathological components.

PATIENT CONCERNS

We describe our experience of a giant high-grade sarcoma with mixed components generated from a solitary fibrous tumor of the pleura in a 67-year-old female patient presenting with cough and left-sided chest pain. The patient had been diagnosed with a pleural mass in the left chest by X-ray about 30 years earlier. However, the tumor was allowed to grow, without surgical intervention, for a long time.

INTERVENTIONS

Thoracic surgeons performed the removal of the giant pleural tumor; the tumor measured 18.0 × 14.5 × 10 cm in size, and was considered a giant tumor generated from the pleura of the left chest cavity.

DIAGNOSES

The surgically removed tumor was solid and light brownish, and included myxoid and arabesque pattern lesions. The tumor also showed hemorrhagic and necrotic lesions. Moreover, spindle cells with less atypia, resembling fibroblasts, were noted. These spindle tumor cells were CD34- and Stat6-positive, suggesting a solitary fibrous tumor. Some of the spindle tumor cells were surrounded by thick collagenous fibers. Considering that the tumor originated from the parietal pleura, the tumor was defined as a solitary fibrous tumor in origin. The tumor also comprised high-grade sarcomatous components; these included lipid-rich, rhabdomyosarcomatous, and pleomorphic components. The high-grade sarcoma component included bizarre tumor cells with severe atypia.

OUTCOMES

Tumor recurrence occurred in the left chest about 4 months after the surgery, and the patient died 8 months postoperatively.

LESSONS

The present case clearly demonstrates that a solitary fibrous tumor can develop into high-grade sarcomatous overgrowth, including lipid-rich, rhabdomyosarcoma, and pleomorphic sarcoma components, if left untreated for a prolonged period. This case provides profound insights about the natural history, histogenesis, differentiation, and malignant transformation of solitary fibrous tumors.

Imaging features of rare mesenychmal liver tumours: beyond haemangiomas

Tumours arising from mesenchymal tissue components such as vascular, fibrous and adipose tissue can manifest in the liver. Although histopathology is often necessary for definitive diagnosis, many of these lesions exhibit characteristic imaging features. The radiologist plays an important role in suggesting the diagnosis, which can direct appropriate immunohistochemical staining at histology. The aim of this review is to present clinical and imaging findings of a spectrum of mesenchymal liver tumours such as haemangioma, epithelioid haemangioendothelioma, lipoma, PEComa, angiosarcoma, inflammatory myofibroblastic tumour, solitary fibrous tumour, leiomyoma, leiomyosarcoma, Kaposi sarcoma, mesenchymal hamartoma, undifferentiated embryonal sarcoma, rhabdomyosarcoma and hepatic metastases. Knowledge of the characteristic features of these tumours will aid in guiding the radiologic diagnosis and appropriate patient management.

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

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

Transsphincteric tumor resection in case of a pararectal solitary fibrous tumor

Transsphincteric resection of rectal tumors was first described about 120 years ago. Nowadays, this approach faded into obscurity due to standardized guidelines and practice in surgical oncology including lymphadenectomy, mesorectal excision and radical dissection of veins. However, transsphincteric resection seems reasonable in some cases, especially if an abdominal approach can be avoided. In the following, we will present and describe the technique of the transsphincteric approach with its variations in rectal surgery in the case of a rare pararectal tumor.

Giant solitary fibrous tumour of the pleura. Case report and review of the literature

Background

Solitary fibrous tumours of the pleura (SFTP) are rare tumours. They are mostly benign. Only around 12% of them are malign ant. In the initial stage they are mostly asymptomatic and by growing they cause chest pain, irritating cough and dyspnoea on account of the pressure created on the surrounding structures. Rare giant tumours have compression symptoms on the mediastinal structures. The condition requires tiered diagnostic radiology. Preoperative biopsy is not successful in most cases. The therapy of choice is radical surgical tumour removal. Malignant or non-radically removed benign solitary fibrous tumours of the pleura additionally require neoadjuvant therapy.

Case report

A 68-year old patient was hospitalized for giant solitary fibrous tumour of the pleura in the right pleural cavity. With its expansive growth the tumour caused the shift of the mediastinum by compressing the lower vena cava, right cardiac auricle as well as the intermediate and lower lobe bronchus. Due to cardiac inflow obstruction and right lung collapse, the patient’s life was endangered with signs of cardio-respiratory failure. After preoperative diagnostic radiology, the tumour was surgically removed. Postoperatively, the patient’s condition improved. No disease recurrence was diagnosed after a year.

Conclusions

Giant solitary fibrous tumour of the pleura may cause serious and life-threatening conditions by causing compression of the pleural cavity with its expansive growth. Early diagnosis of the condition enables less aggressive as well as video-assisted thoracic surgery in patients with significantly better state of health. Large tumour surgeries in cardio-respiratory affected patients are highly risk-associated procedures.

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.

Imaging findings of solitary fibrous tumor in the abdomen and pelvis

PURPOSE

The purpose of this study was to investigate the imaging characteristics of solitary fibrous tumor (SFT) in the abdomen and pelvis.

METHODS

Nine cases of SFT confirmed by surgery and pathology were retrospectively analyzed in terms of computed tomography (CT, eight cases) and magnetic resonance imaging (MRI, one case).

RESULTS

SFT were located in the retroperitoneum (4/9), abdominal cavity (1/9), pelvis (4/9). Eight cases were single (8/9) and one case (1/9) with three tumors. The average tumor size of 11 lesions was 9.7 cm (4.7-20 cm). Nine tumors were round or ovoid, and two lesions were irregular. The CT value of the plain scans ranged from 33 to 43 Hounsfield units (HU, mean 37.6 HU) in five cases. Arterial-phase CT found solid parts demonstrate avid enhancement (eight cases) and five of them presented with multiple circuitous vessels along the periphery with a CT value of 68-89 HU (mean 76.6 HU). In the venous and delayed phases, enhancement was strengthened progressively. The CT values at venous (eight cases) and delayed phases (five cases) were 108-115 and 112-123 HU respectively, with averages of 109.8 and 114.8 HU. Patch or nodular no-enhanced areas were observed in eight cases during the enhanced phases. One case showed isointensity on T1-weighted images and high signal intensity on T2-weighted images accompanied by linear or curvilinear hypointense lines. Intense enhancements along with linear no-enhancement areas are seen in the arterial and venous phases.

CONCLUSION

The possibility of SFT should be considered when a single or multiple masses with sharp border, inhomogeneous density or signal are detected, especially, with inhomogeneous intense enhancement in the arterial phase being maintained in the venous and delayed phases.

Head and neck solitary fibrous tumors: a rare and challenging entity

The objective of this study is to analyze the outcome of treatment for solitary fibrous tumors (SFTs) in the head and neck area. SFTs present as slow-growing masses, often with local compressive symptoms that are difficult to distinguish from other soft-tissue tumors. SFTs are commonly treated using local excision without adjuvant therapy. To date, only heterogeneous small series have been published, documenting the treatment results and outcome with these tumors. Retrospective study of patients with histopathologically confirmed SFT treated at two tertiary referral hospitals between 2004 and 2014. Eight men and four women with histologically confirmed SFT were identified in the records. Their age range was 37-82 years (mean 57.8 years). The mean follow-up period for eight patients was 6.75 years (range 1-24 years). Four patients were lost to follow-up. Sublocalizations were neck (n = 3), orbit (n = 2), paranasal sinus (n = 2), cheek (n = 2), hard palate (n = 1), parotid gland (n = 1), and tongue (n = 1). The first-line treatment for all of the tumors identified was surgical excision. In four cases, the surgical margins were narrow or unclear due to piecemeal resection in the paranasal sinus and orbit (n = 3) or a tumor location deep in the parapharyngeal space (n = 1). Recurrences developed in two of these cases (in the orbit and parapharyngeal space), and the other two patients were lost to follow-up. Radiotherapy and chemotherapy were not administered as first-line treatments. Overall, the local recurrence rate (n = 2/8) was 25 %. The disease-specific survival rate was 100 %. These results are consistent with the literature data and show that safe surgical excision, without opening of the tumor capsule, reduces the risk of local recurrence and leads to a favorable outcome. Tumors in the head and neck often represent a surgical challenge, and wide surgical margins are rarely possible due to the complex three-dimensional anatomic compartments in the region. Head and neck surgeons should therefore be aware that there is an increased risk of recurrence in these patients; tightly scheduled follow-up visits are mandatory for at least 10 years, if not longer. Radiotherapy only appears to be an option in patients with unresectable tumors or when wide surgical excision would cause severe functional morbidity.

Solitary fibrous tumors in abdomen and pelvis: Imaging characteristics and radiologic-pathologic correlation

AIM: To describe the imaging features of solitary fibrous tumors (SFTs) in the abdomen and pelvis, and the clinical and pathologic correlations.

METHODS: Fifteen patients with pathologically confirmed SFTs in the abdomen and pelvis were retrospectively studied with imaging techniques by two radiologists in consensus. Patients underwent unenhanced and contrast-enhanced imaging, as follows: 3 with computed tomography (CT) and magnetic resonance imaging (MRI) examination, 8 with CT examination only, and 4 with MRI examination only. Image characteristics such as size, shape, margin, attenuation or intensity, and pattern of enhancement were analyzed and correlated with the microscopic findings identified from surgical specimens. In addition, patient demographics, presentation, and outcomes were recorded.

RESULTS: Of the 15 patients evaluated, local symptoms related to the mass were found in 11 cases at admission. The size of the mass ranged from 3.4 to 25.1 cm (mean, 11.5 cm). Nine cases were round or oval, 6 were lobulated, and 10 displaced adjacent organs. Unenhanced CT revealed a heterogeneous isodense mass in 7 cases, homogeneous isodense mass in 3 cases, and punctuated calcification in one case. On MRI, most of the lesions (6/7) were heterogeneous isointense and heterogeneous hyperintense on T1-weighted images and T2-weighted images, respectively. All tumors showed moderate to marked enhancement. Heterogeneous enhancement was revealed in 11 lesions, and 7 of these had cysts, necrosis, or hemorrhage. Early nonuniform enhancement with a radial area that proved to be a fibrous component was observed in 4 lesions, which showed progressive enhancement in the venous and delayed phase. No statistical difference in the imaging findings was observed between the histologically benign and malignant lesions. Three patients had local recurrence or metastasis at follow-up.

CONCLUSION: Abdominal and pelvic SFTs commonly appeared as large, solid, well-defined, hypervascular masses with variable degrees of necrosis or cystic change that often displaced adjacent structures.

Clinicopathological findings in a case series of abdominopelvic solitary fibrous tumors

Solitary fibrous tumors (SFTs) represent a rare type of soft tissue tumor. Extrathoracic SFTs (ESFTs) in the soft tissues of the abdominopelvic cavity are extremely rare. Between January 2002 and January 2013, 10 patients were identified with abdominopelvic SFTs at the Northern Jiangsu People's Hospital. The clinicopathological data, treatment and follow-up results were retrospectively analyzed in this study. Patients included four females and six males, whose age ranged between 21 and 75 years (mean, 53.3 years). The maximum diameter of the tumors was 2.5-28 cm (mean, 12.7 cm). Two cases were diagnosed as malignant variants of ESFTs. R0 resection was performed in eight patients, while one patient underwent R1 resection, and one patient received palliative chemotherapy for an inoperable mass. Follow-up time ranged between 6 and 126 months (mean, 50 months). The patient with R1 resection suffered a local relapse, and the patient receiving palliative chemotherapy succumbed to the disease. The remaining eight patients remained free of disease. Abdominopelvic SFTs usually reveal an indolent process, although the majority of tumors in the present study were of giant size when diagnosed. The risk of local recurrence and metastasis correlates with tumor size and the histological status of surgical margins. The preferred treatment is complete resection followed by extended follow-up surveillance.

From pericytes to perivascular tumours: correlation between pathology, stem cell biology, and tissue engineering

PURPOSE

Pericytes were once thought only to aid in angiogenesis and blood pressure control. Gradually, the known functions of pericytes and other perivascular stem cells (PSC) have broadly increased. The following review article will summarize the known functions and importance of pericytes across disciplines of pathology, stem cell biology, and tissue engineering.

METHODS

A literature review was performed for studies examining the importance of pericytes in pathology, stem cell biology, and tissue engineering.

RESULTS

The importance of pericytes most prominently includes the identification of the perivascular identity of mesenchymal stem cells (or MSC). Now, pericytes and other PSC are known to display surface markers and multilineage differentiation potential of MSC. Accordingly, interest in the purification and use of PSC for mesenchymal tissue formation and regeneration has increased. Significant demonstration of in vivo efficacy in bone and muscle regeneration has been made in laboratory animals. Contemporaneously with the uncovering of an MSC identity for pericytes, investigators in tumour biology have found biologically relevant roles for pericytes in tumor formation, lymphovascular invasion, and perivascular tumor spread. As well, the contribution of pericytes to perivascular tumors has been examined (and debated), including glomus tumour, myopericytoma and solitary fibrous tumour/hemangiopericytoma. In addition, an expanding recognition of pericyte mimicry and perivascular tumour invasion has occurred, encompassing common malignancies of the brain and skin.

CONCLUSIONS

In summary, pericytes have a wide range of roles in health and disease. Pericytes are being increasingly studied for their role in tumour formation, growth and invasion. Likewise, the application of pericytes/PSC for mesenchymal tissue engineering is an expanding field of interest.

A huge malignant solitary fibrous tumor of kidney: case report and review of the literature

Virtual slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1603694556107408.

Solitary fibrous tumor (SFT) is a spindle cell neoplasm that rarely occurs in the kidney. Malignant SFT of the kidney is particularly rare. Here, we report a 66-year old woman with a right flank mass that has been proved clinically and radiographically. Grossly, the largest diameter of the mass were measured up to 23 cm, was poorly circumscribed. Approximately 80% of the neoplasm consisted of hyperchromatic and pleomorphic spindled cells surrounding staghornlike blood vessels. Tumor cells frequently had mitoses and necrosis. However, the remainder of the mass was composed of haphazard, storiform or short fascicular arrangements of spindle cells in a loose myxoid to fibrous stroma. Immunohistochemically, we observed diffusely strong CD34 staining and an 85% Ki-67 proliferative index. The tumor partly showed negative CD34 and a 20% proliferative index. To our knowledge, this is the largest malignant renal SFT in the reported literatures and shows an obviously high proliferative index.

Rapid growth of an orbital hemangiopericytoma with atypical histopathological findings

Hemangiopericytoma is a rare vascular tumor that originates from pericytes. The orbit is a rare location for this particular tumor, and corresponds to 0.8% to 3% of all primary orbital tumors. We report a case of a hemangiopericytoma in a 45-year-old man that had an unusual presentation, as a rapidly growing mass in the anterior right inferior orbit. Given that there are no clinical or radiological signs pathognomonic of this tumor, a careful histopathological examination is necessary to confirm the diagnosis. In our case, it presented also with unusual histopathological findings. The clinical features, radiological findings, differential diagnosis and treatment of this challenging entity are reviewed in this case report.

Gene expression profiling of solitary fibrous tumors

Background

Solitary fibrous tumors (SFTs) are rare spindle-cell tumors. Their cell-of-origin and molecular basis are poorly known. They raise several clinical problems. Differential diagnosis may be difficult, prognosis is poorly apprehended by histoclinical features, and no effective therapy exists for advanced stages.

Methods

We profiled 16 SFT samples using whole-genome DNA microarrays and analyzed their expression profiles with publicly available profiles of 36 additional SFTs and 212 soft tissue sarcomas (STSs). Immunohistochemistry was applied to validate the expression of some discriminating genes.

Results

SFTs displayed whole-genome expression profiles more homogeneous and different from STSs, but closer to genetically-simple than genetically-complex STSs. The SFTs/STSs comparison identified a high percentage (∼30%) of genes as differentially expressed, most of them without any DNA copy number alteration. One of the genes most overexpressed in SFTs encoded the ALDH1 stem cell marker. Several upregulated genes and associated ontologies were also related to progenitor/stem cells. SFTs also overexpressed genes encoding therapeutic targets such as kinases (EGFR, ERBB2, FGFR1, JAK2), histone deacetylases, or retinoic acid receptors. Their overexpression was found in all SFTs, regardless the anatomical location. Finally, we identified a 31-gene signature associated with the mitotic count, containing many genes related to cell cycle/mitosis, including AURKA.

Conclusion

We established a robust repertoire of genes differentially expressed in SFTs. Certain overexpressed genes could provide new diagnostic (ALDH1A1), prognostic (AURKA) and/or therapeutic targets.

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.

De novo malignant solitary fibrous tumor of the kidney

The kidney is a relatively infrequent site for solitary fibrous tumor (SFT). Among the previously reported cases, only two cases of malignant renal SFT developing via dedifferentiation from a pre-existing benign SFT have been reported. Here we reported a case of de novo malignant renal SFT clinically diagnosed as renal cell carcinoma in a 50-year-old woman. The tumor was circumscribed but unencapsulated and showed obvious hemorrhagic necrosis. Microscopically, the tumor was composed of patternless sheets of alternating hypercellular and hypocellular areas of spindle cells displaying mild to moderate nuclear atypia, frequent mitoses up to 8 per 10 high power fields, and a 20% Ki-67 proliferative index. Immunohistochemical studies revealed reactivity for CD34, CD99 and vimentin, with no staining for all other markers, confirming the diagnosis of SFT. No areas of dedifferentiation were seen after extensive sampling. Based on the pathologic and immunohistochemical features, a diagnosis of de novo malignant renal SFT was warranted. Our report expands the spectrum of malignant progression in renal SFTs. Even though this patient has been disease-free for 30 months, long-term follow-up is still mandatory.

Somatic and visceral solitary fibrous tumors in the abdomen and pelvis: cross-sectional imaging spectrum

Solitary fibrous tumors (SFTs) are a unique group of mesenchymal neoplasms of fibroblastic or myofibroblastic origin. These tumors were originally described as "benign fibrous mesotheliomas" of the pleural cavity and were erroneously thought to be confined to the serosal surfaces (due to a putative mesothelial or submesothelial origin). It is now established that SFTs are ubiquitous neoplasms with both pleural and extrapleural distribution. Extrapleural SFTs commonly occur in middle-aged adults and manifest as asymptomatic, slow-growing, large tumors. Fewer than 5% of patients with SFTs present with symptomatic hypoglycemia. SFTs are histopathologically diverse with a variable admixture of fibroblasts or myofibroblasts, numerous thin-walled vessels, and dense fibrosis. Tumors previously categorized as hemangiopericytomas are now considered cellular variants of SFTs. At imaging, SFTs demonstrate remarkable heterogeneity, with variable degrees of enhancement, necrosis, or hemorrhage. Although most extrapleural SFTs have a benign clinical course, 10%-15% of these tumors demonstrate aggressive behavior in the form of recurrence or malignancy.

[Primary malignant solitary fibrous tumor/hemangiopericytoma of the parotid gland]

Solitary fibrous tumor (SFT) was first described in the pleura by Lietaud in 1767; later in 1870, Wagner described the localized nature of this type of tumor and Klemperer and Rabin classified pleural tumors into two types: diffuse mesotheliomas and localized mesotheliomas. Recent years have seen the redefinition of this neoplasm, due to better technology; it is now proven that this neoplasm may have multiple different extrapleural origins including the head and neck regions. This diversity of locations is related to the particular mesenchymal histogenesis of SFT which allows its development from very unusual sites such as the salivary glands (SGs). In this particular site, this neoplasm is very infrequent and most of reported cases refer to benign disease, with just one case informed so far of primary malignant SFT.

New insights into the hemangiopericytoma/solitary fibrous tumor spectrum of tumors

PURPOSE OF REVIEW

This review provides an overview of the hemangiopericytoma/solitary fibrous tumor (HPC/SFT) spectrum of tumors, focusing on the histopathologic characteristics, clinical features, diagnosis, and treatment of HPC/SFT.

RECENT FINDINGS

Due to the relatively insensitive nature of HPC/SFT to radiotherapy and cytotoxic chemotherapy, new therapies are needed for treatment of advanced disease. Inhibition of angiogenic pathways may provide a novel therapeutic mechanism for targeting this malignancy. Combination therapy with temozolomide and bevacizumab has recently emerged as a potentially promising regimen for HPC/SFT.

SUMMARY

With many novel targeted therapies currently in development for soft tissue sarcomas, a better understanding of the molecular pathogenesis and aberrations of HPC/SFT is needed to determine optimal therapeutic agents. Identifying appropriate targets and designing rational prospective clinical trials will not only improve treatment of HPC/SFT but will also lead to a new paradigm of personalized, targeted therapy.

Undifferentiated Perivascular Cells in Myxoid Mesenchymal Tumors: An Ultrastructural Study

The current WHO classification of soft tissue tumors is based on the lineage of differentiation of the proliferating cells. Since mature mesenchymal cells have a broad phenotypic plasticity it has been considered unnecessary to recur to a hypothetical stem cell to explain the origin of these neoplasms. In spite of this assumption, the target cell of the oncogenic mutations in mesenchymal tumors is still a controversial item. Myxoid mesenchymal tumors constitute a heterogeneous group of neoplasms sharing in an ample mucinous matrix that separates neoplastic cells and facilitates their single submicroscopic study under electron microscopy examination. The authors have studied, by electron microscopy, 74 myxoid mesenchymal tumors, including a large variety of nosologic entities, to assess their madurational gradient. In 43 of 74 cases, a common element has been found: medium-sized cells, with high nucleo-cytoplasmic ratio, lacking lineage specific features, which were arranged around the capillary vessels. In some cases, the authors were able to demonstrate gradual differentiation in these cells, as they moved away from the vessels. These features support the hypothesis that at least some mesenchymal tumors originate from perivascular undifferentiated cells. In addition, the findings might contribute to define both topographic and morphologic characteristics of adult stem mesenchymal cells.

Hemangiopericytoma of the cerebellopontine angle: a case report and review of the literature

BACKGROUND

Intracranial hemangiopericytoma represents a rare intracranial tumor that is typically difficult to distinguish from meningioma based on clinical presentation and radiographic findings. These inherently aggressive neoplasms have been observed to occur in numerous intracranial compartments; however, isolated involvement of the CPA is essentially unreported. The authors present a case of a young lady with presumed right acoustic schwannoma, which proved to be HPC on histopathology. The case is described; and a review of the literature pertaining to the diagnosis, optimal management, and follow-up for these lesions is provided.

CASE DESCRIPTION

A 37-year-old Asian woman presented with a 7-month history of right ear and mandible numbness, as well as subjective hearing loss involving the right ear. Magnetic resonance imaging demonstrated the presence of a homogeneously enhancing extraaxial lesion in the right CPA, radiographically suggestive of an acoustic schwannoma. The lesion proved to be an intracranial HPC on histologic sections. Review of the neurosurgical literature yielded only one prior detailed account of HPC confined to the CPA. The patient underwent right retrosigmoid craniotomy for gross total resection of the mass, followed by stereotactic radiotherapy several weeks postoperatively.

CONCLUSION

Given the fundamentally different treatment approach for HPCs over other more common CPA tumors, it is imperative that the treating surgeon consider this rare diagnosis when evaluating patients with lesions localized to this area. Specifically, gross total resection, followed by adjuvant SRT, provides patients with the highest probability for disease-free survival, based on current evidence in the neurosurgical literature.

A solitary fibrous tumor in the broad ligament of the uterus

Solitary fibrous tumor (SFT) is a rare mesenchymal tumor that occurs preferentially in the pleura. Although it has been described at some extrathoracic sites, its occurrence in the female genital tract is extremely rare. We are the first to report on an unusual case of a large (14cm in the largest diameter) SFT localized in the broad ligament of the uterus in a 50-year-old woman. The patient underwent surgical tumor extirpation and has remained well without any sign of local tumor recurrence after 6 years of follow-up. We discuss the clinical aspects, the gross macroscopic appearance, the histologic findings, and the differential diagnosis, and provide a review of the literature.

Pulmonary lipomatous hemangiopericytoma: report of a rare tumor and comparison with solitary fibrous tumor

Lipomatous hemangiopericytoma is a rare mesenchymal tumor showing areas of lipid-containing cells admixed with a spindle-cell component. Like other hemangiopericytomas, it shows a similar vascular pattern to solitary fibrous tumor and, partly for this reason, it and other hemangiopericytomas have been subsumed into solitary fibrous tumor. The present study provides a comprehensive documentation of a single case of pulmonary lipomatous hemangiopericytoma of the lung, the first to be described at this site, and compares it with solitary fibrous tumor, in terms of clinical, histological, immunohistochemical, ultrastructural, and cytogenetic findings. Apart from the lipid-laden-cell component, pulmonary lipomatous hemangiopericytoma and solitary fibrous tumor were similar histologically. Bcl-2 was positive in both. CD34 was minimally expressed in pulmonary lipomatous hemangiopericytoma, which possessed some non-descriptive intercellular junctions, a feature shared by solitary fibrous tumor, which was CD34 positive. However, one of the latter was rich in gap junctions, a feature consistent with strong connexin (Cx) 43 staining and the existence, hitherto unappreciated, of a CD34/Cx43-positive tumor cell network. In pulmonary lipomatous hemangiopericytoma, chromosomal deletions of 43-44, X, -Y were found. In solitary fibrous tumor, 46, XY, del(13)(q?) abnormalities and abnormalities involving chromosome 10 were frequently observed. These similarities and differences are discussed in the context of the currently favored diagnostic fusion of hemangiopericytoma and solitary fibrous tumor.

Solitary fibrous tumours of the infratemporal fossa. Two case reports

INTRODUCTION

The solitary fibrous tumour is a rare neoplasm originally described as a pleural tumour. An increasing number of different locations are described in the literature. Among the extrapulmonary sites, head and neck can be involved and particularly the nose, the paranasal sinuses, the submandibular region, the parapharyngeal space and the infratemporal fossa.

MATERIAL

Two cases, one of a young woman and another of an elderly gentleman are reported, each presenting with a solitary fibrous tumour of the infratemporal fossa. In one case an antero-lateral, transcranio-facial and in the other, a transmandibular approach (without labiotomy) were utilized. In both cases complete excision of the lesion and good cosmetic results were achieved.

RESULTS

Both patients were free from the disease for 5 postoperatively.

CONCLUSIONS

To date, very few cases of solitary fibrous tumour of the craniofacial complex have been observed to enable an accurate prognosis. Thus, treatment and follow-up should be identical to fibrous tumours located in other areas.

Pleural malignant solitary fibrous tumor with sarcomatous overgrowth showing PDGFRbeta mutation

Pleural malignant solitary fibrous tumors (SFTs) are uncommon, and little is known about their histogenesis and molecular features. We report a case of pleural SFT with sarcomatous overgrowth that showed expression for PDGFRbeta and a missense mutation on exon 18 of the PDGFRbeta gene. The involvement of the PDGFRbeta gene in SFT is compatible with a pericytic derivation, also supporting a possible role of this tyrosine kinase in malignant transformation and in the adoption of novel molecular therapies.

Solitary fibrous tumour and haemangiopericytoma: evolution of a concept

Haemangiopericytoma (HPC) was described in 1942 by Stout and Murray as a distinctive soft tissue neoplasm, presumably of pericytic origin, exhibiting a characteristic well-developed "staghorn" branching vascular pattern. Over the years, it appeared that this growth pattern was a non-specific one, shared by numerous, unrelated benign and malignant lesions, and that HPC was better considered as a diagnosis of exclusion. Three categories of lesion may now be individualized within the heterogeneous group of HPC-like neoplasms. The first category corresponds to those non-HPC neoplasms that occasionally display HPC-like features (e.g. synovial sarcoma). Lesions belonging to the second category show clear evidence of myoid/pericytic differentiation and correspond to true HPCs. They generally show a benign clinical course, and include glomangiopericytoma/myopericytoma, infantile myofibromatosis (previously called infantile HPC), and a subset of sinonasal HPCs. The third category is the solitary fibrous tumour (SFT) lesional group, which includes fibrous-to-cellular SFTs, and related lesions such as giant cell angiofibromas and lipomatous HPCs. In practice, any HPC-like lesion can be allocated to one of these categories, leaving the ill-defined "haemangiopericytoma" category empty.