Malignant Solitary Fibrous Tumor of the Kidney: Report of a Case and Comprehensive Review of the Literature

Solitary Fibrous Tumor of the Kidney With Pure Round Cell Features: A Case Report With Review of Literature

Solitary fibrous tumor (SFT) is a rare mesenchymal neoplasm known to occur at various soft tissue and visceral locations. Kidney is a rarely reported site for these tumors. Most of the SFTs described in the kidney exhibit a classical CD34-positive patternless spindle cell histology. Focal round cell morphology is seldom reported. Herein, we describe a 48-year-old male patient with renal SFT. This tumor had pure round cell morphology with a CD34-/STAT6+ immunophenotype. Fluorescent in situ hybridization and a multiplexed sequencing assay performed on an Illumina® HiSeq 4000 platform revealed NAB2 and STAT6 gene rearrangement. Renal tumors with round cell morphology are diagnostically challenging and SFT is not often considered in the differential diagnosis of a round cell tumor of the kidney. Moreover, a CD34-negative profile can be rather confounding while diagnosing such lesions. In such scenarios, a strong nuclear STAT6 immunostaining is extremely helpful in clinching the diagnosis. SFT should always be considered in the differential diagnosis of round cell tumors of the kidney due to significant diagnostic and therapeutic implications.

CD34-Negative Malignant Renal Solitary Fibrous Tumor: Case Report and Diagnostic Insights

Solitary fibrous tumors (SFTs) are rare fibroblastic neoplasms with diverse biological behaviors and widespread distribution. Primary renal SFTs are uncommon, and their malignant variants, especially those that are CD34 negative, are even rarer. This study presents a case of malignant renal SFT in a 57-year-old female, focusing on its immunomorphological features. On gross examination, the tumor's large size (11.5 cm) was remarkable. Microscopic analysis showed high cellularity, diffuse sheets of moderately pleomorphic ovoid cells, prominent staghorn vessels, tumor cell necrosis, and a high mitotic count. Immunohistochemistry revealed strong positivity for STAT6, vimentin, and Bcl-2 and, notably, negativity for CD34. The presence of the NAB2::STAT6 gene fusion was confirmed through fluorescence in situ hybridization. This case emphasizes the need to consider SFT in the differential diagnosis of unusual renal tumors, even when CD34 is negative. The infrequency, morphological diversity, and resemblance to other tumors make diagnosing renal SFTs challenging. Accurate identification and classification as benign or malignant are crucial for proper clinical management and prognosis.

A Rare Case of Solitary Fibrous Tumor of the Kidney

Solitary fibrous tumor (SFT), originally described in the pleura, is a rare mesenchymal neoplasm characterized by a wide spectrum of clinical presentations and histopathological features. Over the years, SFTs have been reported in various anatomical locations, including soft tissues, visceral organs, and, uncommonly, the kidney. While SFTs primarily arise from the pleura, their occurrence in the kidney is an infrequent phenomenon, accounting for a minute fraction of all renal tumors. This case report presents a unique instance of a solitary fibrous tumor originating in the kidney, highlighting its clinical, radiological, and histopathological characteristics, as well as the challenges associated with accurate diagnosis and appropriate management. The rarity of such cases underscores the importance of comprehensive evaluation and awareness among clinicians and pathologists to ensure timely diagnosis and effective treatment strategies. Here, we report a case of SF of the kidney (SFT-K) located in the renal pelvis in a 39-year-old Caucasian female.

Case report: Solitary fibrous tumor of the kidney with a NAB2-STAT6 fusion gene

Background

Solitary fibrous tumor (SFT) is a rare spindle cell neoplasm that mostly originates from the pleura, and accounts for only 2% of all soft tissue tumors. Moreover, the cases of SFT of the kidney are rarely reported. Here, we report a typical case of kidney SFT, which was consistent with other reported cases. This case further expands on existing diagnostic methods of SFT and explains the importance of STAT6 mutations in SFT.

Case Summary

We report a typical case of SFT of the kidney. A 34-year-old woman presented to the urinary surgery department after physical examinations were suggestive of a urologic neoplasm. Further relevant imaging investigations suggested a renal tumor with benign behaviors. The patient was diagnosed with a kidney tumor suspected to be SFT and underwent laparoscopic radical left nephrectomy. Postoperative pathological immunohistochemical tests showed positivity for Signal Transducer and Activator of Transcription 6(STAT6), CD-34, CD-99, and Bcl-2, thus confirming the diagnosis of SFT. Combined with the results of genetic testing of the patient, the tumor was indicated to carry NGFI-A-Binding protein 2(NAB2): exon 6—STAT6: exon 16 mutation sites, which confirmed our diagnosis. The patient recovered quickly without any clinical evidence of incomplete resection. She has been followed-up for more than a year and will continue to be reviewed every three months to observe the final outcomes.

Conclusion

Solitary fibrous tumor is difficult to differentiate from other renal tumors. CT imaging, STAT6 immunostaining and gene profiling are valid investigations to establish the diagnosis.

Solitary Fibrous Tumor of Internal Jugular Vein: An Extremely Rare Entity with Review of Literature

Solitary fibrous tumor (SFT) is an unusual spindle cell neoplasm that commonly arises from pleura. In the last decade, multiple case reports have described its diverse occurrence in extrapleural locations involving almost every anatomic site. Intravascular SFT is extremely rare and has been reported in inferior vena cava and renal vein only, to the best of our knowledge. SFT of the internal jugular vein has never been reported. We present a case of a SFT arising from internal jugular vein with extraluminal exophytic component extending into supraclavicular fossa. It should also be considered as a differential diagnosis for neoplasm arising from the internal jugular vein.

BCOR Overexpression in Renal Malignant Solitary Fibrous Tumors: A Close Mimic of Clear Cell Sarcoma of Kidney

BCOR immunoreactivity is a sensitive and highly specific marker for clear cell sarcoma of the kidney (CCSK). However, a subset of adult renal sarcomas which overexpress BCOR are negative for BCOR genetic alterations, including BCOR gene fusions or BCOR-internal tandem duplication, and thus remain unclassified. We report 5 such undifferentiated renal/perirenal sarcomas which raised the differential diagnosis of CCSK due to their morphologic appearance and strong BCOR immunoreactivity, but which on RNA sequencing proved to be malignant solitary fibrous tumors (SFTs). The neoplasms occurred in patients at an age range of 30 to 62 years. Three patients were females and 2 male. Four were primary renal neoplasms while one was perirenal. All 5 neoplasms were cellular, nonpleomorphic, undifferentiated sarcomas with branching capillary vasculature composed of primitive round to ovoid neoplastic cells with scant cytoplasm and nuclei having fine, evenly dispersed chromatin. None of the cases demonstrated the typical hyperchromatic fusiform nuclei, prominent collagen deposition, or hemangiopericytomatous vasculature of SFT. All 5 cases were strongly immunoreactive for BCOR. Three cases were CD34 negative, where the other 2 were only focally CD34 positive. STAT6 was subsequently found to be positive by immunohistochemistry in all 5 cases. In summary, we report a previously unrecognized mimic of CCSK: malignant SFTs with an undifferentiated/small round cell phenotype along with branching capillary vasculature, strong immunoreactivity for BCOR, and minimal or no immunoreactivity for CD34. As CCSK is treated with a specific chemotherapy regimen, this distinction has therapeutic implications.

Solitary fibrous tumor of the kidney: A case report

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Solitary fibrous tumor is a rare entity, representing 2% of all soft tissue tumors.

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The disease is usually described in the thoracic cavity, only 105 cases of renal solitary fibrous tumor have been reported.

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Solitary fibrous tumors are usually asymptomatic thus they are diagnosed as renal cell carcinoma and treated as such.

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Typical immunohistochemical characteristic is a high positivity for CD34.

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As solitary fibrous tumor has a malignant potential, careful follow-up is mandatory.

Introduction

Solitary fibrous tumor (SFT) is rare, representing 2% of all soft tissue tumors and is usually described in the thoracic cavity. Only 105 cases of renal SFT have been reported.

Case presentation

A 55-year-old men with lower urinary tract symptoms, had a routine renal ultrasound which showed a cortical mass of the left kidney measuring 36 × 23 × 39 mm, with peripheral enhancement, and a central fluid collection on CT. On MRI, it was iso-intense to the kidney in T1 and hyper-intense with restricted diffusion in T2 images. The diagnosis of renal cell cancer was likely and an open partial nephrectomy was performed. Microscopic examination showed a mesenchymal neoplasm with long spindle cell and Immunohistochemical staining positive for CD34 and Bcl-2 confirming the diagnosis of SFT.

There was no evidence of tumor recurrence or metastasis nine months after discharge.

Discussion

Up to now, only 105 cases of occurring renal SFT have been reported. SFTs are usually asymptomatic when they have a small size, that’s why the diagnosis is often delayed. Blood tests do not have any diagnostic value. Imaging features are not specific for the diagnosis of SFT which are diagnosed as renal cell carcinoma and treated as such. Typical immunohistochemical characteristic is a high positivity for CD34. As SFT has a malignant potential, careful follow-up is mandatory,searching for local recurrence or metastasis which was reported in few cases.

Conlusion

SFTs are indolent tumors and are usually diagnosed as renal cell carcinomas preoperatively and the final diagnosis is always based on immunohistochemical study.

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.

Recurrence of multiple metastases after surgical removal of a primary malignant solitary fibrous tumor from the main bronchus: A case report

RATIONALE

Limited knowledge is available regarding solitary fibrous tumors (SFTs), about 15% of which are malignant. In particular, the long-term survival of patients with malignant SFTs (mSFTs), the disease course, and the potential for recurrence of second primary tumors or distant metastases are largely undetermined.

PATIENT CONCERNS

We report a rare case in which an mSFT was found at the main bronchus of the right lung of a 37-year-old man.

DIAGNOSIS

The tumor cells of mSFT were spindle-shaped and expressed antigen Ki-67, B-cell lymphoma 2, cluster of differentiation 31, and vimentin.

INTERVENTIONS

A total pneumonectomy was performed.

OUTCOMES

The patient developed fibrosarcoma of the small intestine at 6 months, as well as extensive pleural and peritoneal metastases at 1 year, after removal of the primary mSFT from the right main bronchus.

LESSONS

From these findings, we expect that patients with primary mSFT, especially of the lung, have a high potential to develop second tumors or distant metastases. Close monitoring after surgery is necessary to improve the outcomes of these patients.

Malignant Solitary Fibrous Tumor of the Renal Vein Presenting as a Giant Renal Artery Aneurysm: A Case Report and Review of Literature

OBJECTIVES

To discuss an unusual presentation of solitary fibrous tumor (SFT) as well as the first description of SFT originating from the renal vein.

CASE REPORT

In this article, we report the case of a 56-year-old man who presented with nonspecific epigastric pain and was found on computed tomography to have a large 10-cm renal artery aneurysm with evidence of contained rupture, segmental ischemia of the kidney, and suggestion of renal vein thrombosis. This was treated by a multidisciplinary team of urologists, vascular surgeons, and interventional radiologists with both renal artery coil embolization and radical nephrectomy. The thrombosis was found on pathologic review to be a malignant SFT originating from the renal vein with likely erosion into the renal artery.

CONCLUSION

This report describes the first case of SFT originating from the renal vein and demonstrates the potential for mimicry as a giant renal artery aneurysm.

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 of the Kidney. A Propos of a Case

Solitary Fibrous Tumors (SFT) are rare spindle cell neoplasm that typically originate from the pleura. However, cases of the SFT are described with origin in other organs, including the urinary and genital apparatus. Within the kidney, except from the renal pelvis, only 19 cases of SFT are described and such rarity of localization makes the histogenesis and the prognosis of the tumor rather unknown. We report the case of a 72-year-old lady who attended our Unit for a mass that was clinically palpable at the level of the left hemiabdomen. The tomodensitographic test indicated a 19cm-diameter mass of likely pertinence of the middle bystender of the left kidney. She had undergone left radical nephrectomy. The histological examination highlighted a solitary fibrous tumor (SFT): the presence of hypercellularity, of cellular pleiomorphism and of a high number of mitosis has led to a histological diagnosis of malignancy for the neoplasm analyzed. The SFT are of rare clinical comparison: this does not allow for a deep knowledge of the lesion histogenesis and prognosis; moreover, the clinical behavior should be more precisely defined.

Conservative approach for a solitary fibrous tumor of the kidney

INTRODUCTION

Solitary fibrous tumor (SFT) of the kidney represents a rare neoplasm, and its malignant potential seems to be scarce. Classically, a radical nephrectomy is regarded as the treatment of choice for this condition.

CASE REPORT

We present the case of a 37-year-old male patient who underwent left robotic clampless partial nephrectomy of an SFT of the kidney. Our patient has been followed-up carefully, and at 15-month examination, he is free of recurrence. This is the second case of an SFT managed through a conservative approach.

CONCLUSIONS

In our opinion, according to tumor's dimensions, partial nephrectomy may be considered for treating small SFTs.

Solitary Fibrous Tumor of the Kidney Developing Local Recurrence

Solitary fibrous tumor (SFT) of the kidney is a rare entity and usually displays a favorable prognosis. We herein report a second case of renal SFT developing local recurrence. A 50-year-old man was referred to our hospital because of a left renal mass. An abdominal CT detected a large renal tumor and radical nephrectomy was performed with a possible diagnosis of renal cell carcinoma. The resected tumor size was measured at 17 × 11 × 8 cm. Grossly, necrosis was observed in central lesion of the tumor but hemorrhage was not observed. Microscopically, the tumor consisted of spindle-shaped cells with scant cytoplasm accompanied by hyalinized collagenous tissue, which displayed hemangiopericytomatous patterns. The cellularity was normal and nuclear pleomorphism was not observed. Ki-67 labeling index was less than 3%. The pathological diagnosis of SFT was made without obvious malignant findings. Three years after the surgery, a follow-up CT scan detected a mass lesion in the tumor bed. Surgical resection was performed and the resected tumor was compatible with local recurrence of the SFT without obvious malignant findings. Renal SFT should be carefully monitored even in the absence of obvious malignant findings.

Solitary Fibrous Tumor of the Kidney: A Case Report and Literature Review

Solitary fibrous tumors are neoplasms of mesenchymal origin that may occur virtually in any body part, most commonly arising from the pleura. Solitary fibrous tumor of the kidney is exceptionally rare, and limited clinical knowledge regarding its behavior makes prognosis of the neoplasm difficult. We report a case of solitary fibrous tumor of the left kidney and describe its clinical, imaging, and pathological features.

Metachronous Malignant Solitary Fibrous Tumor of Kidney: Case Report and Review of Literature

Solitary fibrous tumors are well described in the pleura, but rare extra-pleural neoplasms have been reported. We describe a patient with a solitary left renal fibrous tumor who after undergoing a nephrectomy, presented 8 years later with a contralateral metachronous solitary fibrous tumor. Malignant metastatic extra-pleural solitary fibrous tumors are extremely rare, and to our knowledge, this is the first case of contralateral recurrence of solitary renal fibrous tumor. The patient underwent a robotic assisted partial nephrectomy of the right renal mass. Both tumors showed overlapping histopathology.

A GRIA2 and PAX8-positive renal solitary fibrous tumor with NAB2-STAT6 gene fusion

Solitary fibrous tumor (SFT) is a rare neoplasm composed of mesenchymal-derived spindle cells. Although SFT occurs anywhere in the body, they most frequently affects the thoracic region. Here, we reported an extremely rare case of an extrathoracic SFT occurring primarily in the kidney. To our knowledge, little information has been described on the immunohistochemistry (IHC) and genetics of renal SFT.

A 41-year old Japanese female came to our hospital for further examination of a left kidney mass detected incidentally with ultrasound. Extensive investigation of the tumor, including physical, laboratory, and image examinations led to a clinical diagnosis of renal cancer (cT1aN0M0), which were in most parts imbedded in the lower polar parenchyma. The patient underwent laparoscopic radical nephrectomy. The mass was diagnosed pathologically as SFT originating from the kidney, but not as renal carcinoma. Microscopically, the tumor was composed of spindle-shape cells distributed variably in dense collagenous stroma and had a focal hemangiopericytomatous staghorn-like vascular pattern. Mitotic figures, atypical structures, necrosis and hemorrhage were not identified. No adjuvant therapies were given postoperatively. The patient has been free of tumor recurrence for 25 months since the surgery. IHC revealed that the tumor diffusely expressed CD34, CD99, Bcl2, PAX8, NAB2, STAT6, and GRIA2. The tumor stained negatively for desmin, S-100, c-Kit, CK-AE1/AE3, CDK4 and MDM2. A NAB2-SATA6 gene fusion was detected in tumor cells by reverse transcription-polymerase chain reaction, direct sequencing, and an in situ proximity ligation brightfield assay. The gene fusion occurred as an 831 bp truncation of exon 2 in NAB2 connected to the beginning of exon 3 in STAT6. We have reported a case of GRIA2 and PAX8-positive SFT occurring primarily in the kidney with such NAB2-STAT6 gene fusion for the first time. Diffuse expression of PAX8 in the tumor might present with a renal origin. Reportedly, benign histology of SFT cannot necessarily predict favorable clinical prognosis. Genetic alterations recently identified in SFT could possibly refer to risk stratification for tumor recurrence. However, malignant preponderance of extrathoracic SFT over thoracic SFT remains unexplained so far. Long-term follow-up after surgery should be performed in the present case.

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.

Primary renal sclerosing epithelioid fibrosarcoma: report of 2 cases with EWSR1-CREB3L1 gene fusion

We report the first 2 genetically confirmed cases of primary renal sclerosing epithelioid fibrosarcoma (SEF), occurring in a 17-year-old boy and a 61-year-old woman. In both cases, the tumors demonstrated the typical epithelioid clear cell morphology associated with extensive hyalinizing fibrosis, raising the differential diagnosis of solitary fibrous tumor, metanephric stromal tumor, and the sclerosing variant of clear cell sarcoma of the kidney. Both neoplasms demonstrated diffuse immunoreactivity for MUC4, a highly specific marker for SEF, and both demonstrated evidence of rearrangement of both the EWSR1 and CREB3L1 genes, which have recently been shown to be fused in this entity. Both neoplasms presented with metastatic disease. Primary renal SEF represents yet another translocation-associated sarcoma now shown to arise primarily in the kidney.

Renal malignant solitary fibrous tumor with single lymph node involvement: report of unusual metastasis and review of the literature

Solitary fibrous tumors are rare mesenchymal spindle cell neoplasms that are usually found in the pleura. The kidneys are an uncommon site and only few cases of renal solitary fibrous tumor exhibit malignant behavior metastasizing to the liver, lung, and bone through the hematogenous pathway.

Suprarenal solitary fibrous tumor associated with a NF1 gene mutation mimicking a kidney neoplasm: implications for surgical management

Solitary fibrous tumor (SFT) is a rare spindle cell neoplasm, usually occurring in the pleura. Pararenal SFT, mimicking an adrenal gland or renal tumor, as here described, is extremely rare. We report a case of a right suprarenal SFT, incidentally discovered by abdominal ultrasound in a 54-year-old woman carrying a point neurofibromatosis 1 (NF1) gene mutation. Preoperative diagnostic work-up was ineffective in evaluating its origin, and an open radical right nephrectomy was therefore undertaken. Immunohistochemical assay showed a positivity for CD34, CD99 and Bcl-2, so suggesting a diagnosis of SFT. According to our knowledge, the association between this type of tumor and NF1 gene mutation has never been described. In cases of pararenal tumors, a more detailed preoperative diagnosis could be useful to better plan the extension of resection, allowing, in selected cases, nephron-sparing surgery. More studies are needed to better analyze the relationship between NF1 gene mutation and SFT.

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.

Malignant solitary fibrous kidney tumor with peritoneal disease: a case report

We report a case of a large malignant solitary fibrous kidney tumor. A complete surgical resection of the primary tumor and peritoneal disease was carried out, and a histological examination confirmed the initial diagnosis. We describe and discuss the characteristics of this rare kidney neoplasm.

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.

Solitary fibrous tumor of the kidney: a case report

Solitary fibrous tumor is a spindle cell neoplasm mostly originating from pleura; however, it has also recently been reported to be extrapleural. A 57-year-old man presented with left lumbal pain. Ultrasonography and computed tomography showed a cystic lesion of 14 × 11 cm with solid areas and septations in middle and lower poles of the left kidney. Radical nephrectomy was performed. Immunohistochemical studies showed strong reactions with CD34 and CD99. A nuclear positivity with Ki-67 was observed in less than 1% of cells. Despite repeated stainings with vimentin, no clear tumor evaluation could be made due to artifacts. The tumor was negative with Bcl-2, desmin, HMB-45, S100, FVIII, and CD31. Histopathological and molecular studies made the diagnosis of a solitary fibrous tumor. The patient is now currently free of disease at the 26th month of followup.

Distant metastasis from benign solitary fibrous tumor of the kidney

Solitary fibrous tumor (SFT) rarely occurs in the kidneys, and only one reported case of renal SFT has shown distant metastasis. We report the second case of renal SFT exhibiting distant metastasis. A 48-year-old man was referred to our hospital because of a right renal mass. An abdominal CT scan detected a large renal tumor, which was suspected to be a renal cell carcinoma. Right radical nephrectomy was performed, and the tumor was found to measure 28 × 18 × 10 cm. The pathological diagnosis was benign solitary fibrous tumor of the kidney. Eight years after the operation, lung and liver metastases developed. Pulmonary segmentectomy and partial hepatectomy were performed. The pathological diagnoses of these resected tissue specimens were compatible with benign SFT.

Malignant solitary fibrous tumor of the kidney: report of the first case managed with interferon

Solitary fibrous tumors of the kidney are extremely rare tumors with unpredictable behavior. We describe a case of a patient with a solitary fibrous tumor of kidney with malignant findings with distant metastasis and nephrectomy managed with subcutaneous interferon achieving 23 months of progression-free survival. To date there is no prospective evaluation of any specific modality of treatment, but the surgical management and long-term followup are the only ones so far recommended strategies in the management of these patients. Studies are awaited with more patients to evaluate the different strategies of systemic therapy reported so far to allow adding survival benefit.

Malignant solitary fibrous tumor in the extremity: Cytopathologic findings

Malignant solitary fibrous tumor (SFT) is an extremely rare neoplasm. There are only rare published accounts of the cytopathologic features of this tumor. We report a case of a 59-year-old woman presented with a 10-year history of a right thigh mass. A preoperative fine needle aspiration (FNA) was performed. Smears were hypercellular, with cohesive and crowded tissue fragments, haphazard cell arrangements and many single cells. The tumor cells were polymorphous, plump spindled or round with often indented or bare nuclei. A differential diagnosis of low grade sarcoma was favored. The diagnosis of malignant SFT is extremely difficult on FNA and must be included in the differential diagnosis of spindle cell neoplasms.

Two malignant solitary fibrous tumors in one kidney: Case report and review of the literature

Malignant solitary fibrous tumors of the kidney are very rare. Two tumors in one kidney is particularly rare and has not been previously reported. Due to the non-specific clinical symptoms, it is difficult but also very significant to give a definite diagnosis. Here, we report a case of two renal masses in one kidney. A 56-year-old man was admitted to our hospital complaining of shortness of breath, weakness, hyperhidrosis and intermittent hypoglycemia of 1-year duration without gross hematuria or lumbago. Imaging studies revealed two masses manifesting as inhomogeneous, with soft-tissue density and having no clear boundaries with the kidney. The patient was initially diagnosed with space-occupying lesions of the left kidney (with suspicions of renal cell carcinoma) and left radical nephrectomy was performed. Histologically, the tumors consisted of ovoid or spindle cells, and a hemangiopericytoma-like pattern and cellular atypia was observed in certain areas. Mitotic figures were more than 4 per 10 high-power fields. Immunohistochemically the tumor cells were positive for CD34, CD99 and vimentin. Accordingly, a diagnosis of malignant solitary fibrous tumor of the left kidney (low-grade malignance) was established. Postoperative follow-up of 10 months did not find tumor recurrence or metastasis and hypoglycemia was resolved with the removal of the tumors.

Cellular metanephric stromal tumor in a postmenopausal woman: a case report with review of the literature

Metanephric stromal tumor (MST) of the kidney is a rare pediatric neoplasm which has rarely been reported in adults. The authors present a case of MST, cellular type, an unreported variant, in a 56-year-old postmenopausal woman. The 9.0-cm tumor was solid, unencapsulated, and well circumscribed, with a firm homogeneous cut surface. The tumor was purely stromal with dense spindle-cell proliferations displaying prominent schwannoma-like architecture, intratumoral angiodysplasia, and entrapped native renal tubules with "onion-skin" tumor collarettes. The tumor stroma expressed CD34, estrogen, and progesterone and did not express desmin, smooth muscle actin, S-100, or TLE-1. Considering the characteristic morphology and immunophenotype, a diagnosis of "metanephric stromal tumor, cellular type," was made. This is an exceptionally rare disease manifestation in an adult patient and the first description of MST with such high stromal cellularity, making this case unique in both clinical and pathological presentation.

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.

Pediatric and adult primary sarcomas of the kidney: a cross-sectional imaging review

There is a wide pathological spectrum of kidney sarcomas that show characteristic histology, ontogeny, and clinical-biological behavior. While leiomyosarcomas commonly arise from the capsule, solitary fibrous tumors and clear cell sarcomas typically show renal sinus and medullary epicenter, respectively. Although distribution and imaging findings of some sarcomas may be characteristic, definitive diagnosis warrants histopathological examination following surgery. Renal sarcomas manifest advanced disease at presentation and portend poor prognosis.

Mesenchymal neoplasms of the kidney in adults: imaging spectrum with radiologic-pathologic correlation

Mesenchymal neoplasms of the kidney in adults cover a wide spectrum with characteristic ontogeny and histologic findings and variable biologic profiles and imaging findings. Benign mesenchymal renal tumors include angiomyolipoma, leiomyoma, hemangioma, lymphangioma, juxtaglomerular cell tumor, renomedullary interstitial cell tumor (medullary fibroma), lipoma, solitary fibrous tumor, and schwannoma. Malignant renal tumors of mesenchymal origin include leiomyosarcoma, rhabdomyosarcoma, angiosarcoma, osteosarcoma, synovial sarcoma, fibrosarcoma, malignant fibrous histiocytoma, and solitary fibrous tumor. Cross-sectional imaging findings for mesenchymal renal tumors in adults are varied. Although angiomyolipomas and lipomas show macroscopic fat, lymphangiomas are cystic in appearance. Renal hemangioma may show phleboliths and a characteristic enhancement pattern. Leiomyoma typically arises from the capsule and causes buckling of the renal cortex. Although osteosarcoma may demonstrate characteristic dense ossification, most renal sarcomas demonstrate imaging features that are indistinguishable from the more common renal cell carcinoma. Although some renal mesenchymal tumors have typical imaging findings, biopsy is warranted to establish a definitive diagnosis. Awareness of the various mesenchymal renal tumors and familiarity with their imaging findings permit optimal patient management.

Malignant solitary fibrous tumor: cytopathologic findings and differential diagnosis

BACKGROUND

Malignant solitary fibrous tumors (SFTs) are extremely uncommon and poorly understood mesenchymal neoplasms. There are only rare published accounts of the cytopathologic features of these tumors, prompting the current study.

DESIGN

All cases of malignant SFT with preoperative fine-needle aspirations (FNAs) from 1999 to 2008 were retrieved from the archives of 3 large teaching hospitals. FNA smears and cell block material including immunoperoxidase stains were reviewed, and the cytologic characteristics were described.

RESULTS

Thirteen cases of malignant SFT were identified in 11 patients. Mean age was 58 years, with a men:women ratio of 1:2.6. The tumors were generally large, with a mean size of 13.4 cm. Cytomorphologic features included mostly hypercellular smears with tissue fragments of monotonous, plump spindled cells with blunt-ended and indented nuclei and fragile, wispy cytoplasm. Also seen were bare nuclei, occasional mitoses, and rare necrosis. Some cases showed a predominance of epithelioid cells, whereas others displayed a loose myxomatous matrix. There was a general lack of single cells. None of the cases was diagnosed accurately as malignant SFT on FNA, and only 6 cases were called malignant or suspicious for malignancy.

CONCLUSIONS

The FNA diagnosis of malignant SFT is extremely difficult and needs histologic material for accurate interpretation. Predominant FNA diagnoses were SFT or spindle cell neoplasm. Malignant SFT must be included in the differential diagnosis of a spindle cell neoplasm of any anatomic site, particularly if it displays features not typical of benign SFT. Immunoperoxidase staining has some utility, mainly in ruling out other neoplasms in the differential diagnosis.