Large solitary fibrous tumor of the kidney: report of two cases and review of the literature

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

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

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.

[Parauterine solitary fibrous tumor: about a case]

Les tumeurs fibreuses solitaires du tractus génital féminin sont extrêmement rares. Nous rapportons le cas d’une patiente âgée de 78 ans qui a présenté une masse pelvienne. L’exploration chirurgicale a montré une tumeur parautérine. L’examen anatomopathologique a conclu à une tumeur fibreuse solitaire avec des signes de malignité. Les suites ont été marquées par le décès de la patiente. Il est important de connaître ces tumeurs dont l’évolution peut être péjorative. Un suivi au long cours doit être recommandé pour les tumeurs résécables.

Unusual benign solid neoplasms of the kidney: cross-sectional imaging findings

Kidney neoplasms are common diseases with varying prognoses depending on the subtype of the tumor. The most common solid lesion of the kidney is renal cell carcinoma, and the treatment is typically surgical removal. With increasing use of cross-sectional imaging in the last two decades, the detection of renal lesions has significantly increased, especially in asymptomatic patients who are scanned for other reasons. In this article, we present the imaging findings of rare solid benign primary kidney neoplasms including renal leiomyoma, reninoma, carcinoid tumor, metanephric adenoma, solitary fibrous tumor of the kidney, lipomatous hemangiopericytoma of the kidney, renal schwannoma, inflammatory myofibroblastic tumor of the kidney, extramedullary hematopoiesis in the kidney, and extranodal renal Rosai-Dorfman disease. Accurate preoperative or prebiopsy diagnoses of these lesions are unusual; however, informed radiologists may sometimes be able to favorably change the patient management and treatment.

Solitary Fibrous Tumor of the Kidney with Massive Retroperitoneal Recurrence. A Case Presentation

Solitary fibrous tumor is an unusual spindle cell neoplasm that usually occurs in the pleura but has also been described in other sites. Renal presentation is rare and only 38 cases of SFT of the kidney have been described until now. Up to 90% of the tumors have benign characteristics. Local retroperitoneal recurrence is extremely rare. We report a case of a large malignant solitary fibrous tumor recurrence after the surgical excision of the primary tumor. Histological examination of the specimen confirmed the diagnosis by revealing highly positive reaction of the neoplasmatic cells for vimentin, CD34, bcl-2 and moderately positive for actin. The rate of Ki67 lied between 2–7%. No adjuvant therapy was given to the patient and he is disease-free with no imaging findings of recurrence or metastasis 9 months after the re-operation.

Renal solitary fibrous tumour: A rare pathological entity

A solitary fibrous tumour (SFT) is a rare mesenchymal cell neoplasm that can develop at any site. SFT of the kidney is extremely rare. Recently, we had a case of solitary fibrous tumour involving the left kidney in a 71-year-old female patient. The SFT was incidentally found by imaging modalities at the time of a physical workup. Computed tomography and retrograde pyelography showed a 4 × 3.5 × 4-cm nodular mass in the middle poles of the left kidney adjacent to the renal pelvis. A laparoscopic radical resection of the left kidney was performed. The tumour was well-circumscribed and composed of a mixture of spindle cells; microscopically, we found dense collagenous bands. Immunohistochemical studies showed strong reactions with CD34, bcl-2 and CD99. A nuclear positivity with Ki-67 was observed in less than 1% of cells. The tumour was negative for desmin, SMA and CD117. Histopathological and immunohistochemical studies confirmed the diagnosis of a solitary fibrous tumour.

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.

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: 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.

Myopericytoma of the kidney

Myopericytoma is a rare, histologically distinctive tumor that shows evidence of differentiation toward perivascular myoid cells. Myopericytoma is largely considered a neoplasm of skin and soft tissues, with examples of this lesion involving visceral sites being extremely limited. We present the clinical and pathologic details of an unusual case of myopericytoma occurring in the kidney. Histologically, the tumor was richly vascularized and composed of a perivascular proliferation of oval to spindle-shaped cells with bland cytologic features. The neoplastic cells were arranged in a concentric fashion around vascular lumina and also surrounded dilated, branching vessels, with a glomangiopericytomatous appearance. Mitotic figures were inconspicuous, and necrosis was absent. Perivascular myoid differentiation was supported by positive immunoreactivity for muscle-specific and smooth muscle actins, and absence of reactivity for desmin. The present case serves to expand the anatomical distribution of myopericytoma and also broadens the spectrum of primary mesenchymal neoplasms that may be encountered in the kidney.

Imaging appearance of solitary fibrous tumor of the abdominopelvic cavity

The computed tomographic or magnetic resonance imaging appearance of solitary fibrous tumors of the abdominopelvic cavity has previously only been presented in the English literature as individual case reports. In this article, we present the cross-sectional imaging appearance of 5 such cases, all of which exhibited highly similar imaging features, including well-circumscribed margins, lack of invasion of adjacent structures, and avid enhancement. In view of these shared imaging features, it may be possible to suggest the diagnosis preoperatively. Given their unpredictable biologic behavior with infrequent reports of recurrent or metastatic disease, complete surgical excision and long-term follow-up for these lesions is recommended.

MR imaging of renal masses: correlation with findings at surgery and pathologic analysis

Magnetic resonance (MR) imaging is useful in the characterization of renal masses. The MR imaging manifestations and pathologic diagnoses of 82 renal masses were reviewed and correlated. The MR imaging appearance of clear cell type renal cell carcinoma varies depending on the presence of cystic components, hemorrhage, and necrosis. Papillary renal cell carcinomas appear as well-encapsulated masses with homogeneous low signal intensity on T2-weighted images and homogeneous low-level enhancement after the intravenous administration of contrast material, or as cystic hemorrhagic masses with peripheral enhancing papillary projections. Transitional cell carcinoma may be seen as an irregular, enhancing filling defect in the pelvicaliceal system or ureter. Lymphomatous masses are usually hypointense relative to the renal cortex on T2-weighted images and enhance minimally on delayed gadolinium-enhanced images. Bulk fat is a distinguishing feature of angiomyolipoma. Oncocytoma has a variable and nonspecific appearance at MR imaging. MR imaging findings may allow the characterization of various renal masses and can provide valuable information for their clinical management.

Solitary fibrous tumor of the kidney

Solitary fibrous tumors are rare spindle cell neoplasms usually arising in the pleura. They have, however, also been reported at extrapleural locations. Solitary fibrous tumor (SFT) of the kidney is rare. Despite its rarity, histological diagnosis of solitary fibrous tumor is crucial to avoid misdiagnosis with other more aggressive tumors arising in the kidney. We report a solitary fibrous tumor of the left kidney that presented as a malignant tumor in a 51-year-old woman, and include clinical and radiographic findings. The tumor was well circumscribed and composed of spindle cells in a collagenous stroma. Immunohistochemistry showed reactivity for vimentin, CD 34, BCL-2 protein and CD99. Immunohistochemical stains for cytokeratin, S-100, desmin, alpha-smooth muscle actin and HMB-45 were negative. A diagnosis of SFT was made based on light microscopy and immunohistochemistry.

Mixed epithelial and stromal tumor of the kidney: a case report

The descriptive term "mixed epithelial and stromal tumor of the kidney" was recently proposed for a group of renal tumors characterized histologically by a mixture of stromal and epithelial proliferation. It is a rare benign neoplasm of the kidney which has been reported under various names such as adult type mesoblastic nephroma or others. We report a case of mixed epithelial and stromal tumor in a 47 yr old female patient presenting as a partly cystic and partly solid renal mass. Microscopically, the tumor exhibited spindle cell component in solid portion and epithelial proliferation around microcystic areas. Immunoreactive profiles and ultrastructural examination suggested myofibroblastic nature of the stromal cells. We believe this case exemplifies a unique adult renal tumor displaying both epithelial and stromal neoplastic component and has a few unusual features worthy of attention.

Solitary Fibrous Tumor of the Uterus

OBJECTIVE

A solitary fibrous tumor is an uncommon soft-tissue tumor and rarely occurs in the uterus. We present such a case.

CASE REPORT

A 78-year-old woman presented with low abdominal pain, and pelvic computed tomography showed a pelvic mass attached to the uterus. As malignancy could not be ruled out, exploratory laparotomy with complete surgical staging was performed. The results of frozen section showed benign mesothelioma-like tumor. Unexpectedly, further histopathologic results of the lesion revealed a solitary fibrous tumor, an outcome that was subsequently confirmed by means of CD34 immunohistochemical stain.

CONCLUSION

The behavior of solitary fibrous tumors arising from the uterus is difficult to evaluate; therefore, complete surgical excision featuring clear margins and comprehensive follow-up is recommended.

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

Renal solitary fibrous tumors (SFTs) have been reported infrequently. We report a 76-year-old man with a left renal mass that had previously been shown radiographically to be stable, but was now growing. Grossly, the mass measured 12 cm, was poorly circumscribed, and invaded beyond the renal capsule. Approximately 10% of the neoplasm consisted of haphazardly arranged spindle cells admixed with dense collagenous bands, which is typical of benign SFT. However, the remainder of the mass was composed of pleomorphic, spindled sarcoma cells with frequent mitoses and foci of necrosis. Immunohistochemically, we observed CD34 labeling in the benign SFT component with loss of expression in the sarcomatous component, focal labeling for Bcl-2 protein in both areas, and absence of labeling for cytokeratin, renal cell carcinoma marker, S100 protein, CD117, and muscle markers in both areas. To our knowledge, this is the first reported case of malignant renal SFT, likely representing transformation from a histologically documented benign SFT component.

Tumor fibroso solitário do rim: descrição de caso

Apresentamos um caso de tumor renal num paciente de 27 anos de idade, que foi submetido a estudo de imagem por tomografia computadorizada e ressonância magnética. As características radiológicas da massa induziam para um diagnóstico de tumor renal maligno de origem intraparanquimatosa. No entanto, o estudo histopatológico revelou tumor fibroso solitário benigno originário da pelve e porção calicial do rim direito.

Magnetic Resonance Imaging Findings in Solitary Fibrous Tumor of the Kidney

The magnetic resonance imaging findings in a patient with a large solitary fibrous tumor (SFT) of the kidney originating in the renal capsule are presented. SFT of the kidney is a rare, usually benign tumor with indolent clinical behavior. MRI revealed a diffusely hypointense mass on T2-weighted images without central necrosis despite the large size of the lesion. These imaging features, atypical for renal cell carcinoma, can suggest the diagnosis of SFT and may be an indication for attempting nephron-sparing surgery.

Usefulness of immunohistochemistry in delineating renal spindle cell tumours. A retrospective study of 31 cases

AIMS

To assess the usefulness of immunohistochemistry in delineating tumour diagnoses on a series of morphologically diagnosed renal spindle cell tumours (RSCTs).

METHODS AND RESULTS

Formalin-fixed paraffin-embedded tissues from 31 morphologically diagnosed tumours were reinterpreted in light of newly obtained immunohistochemical information. By morphology, six had originally been classified as sarcomatoid carcinoma, five as spindle cell tumour (NOS), four as sarcoma (NOS), three as leiomyoma, three as leiomyosarcoma, and one each as fibrous polyp, hamartoma, neurilemmoma, mesoblastic nephroma, medullary fibroma, angiomyolipoma, haemangiopericytoma, malignant rhabdoid tumour, malignant Triton tumour, and carcinosarcoma. The application of immunohistochemistry verified the original diagnosis in 18 cases (18/31, 58%), confirming the diagnosis of sarcomatoid renal carcinoma (4/6), leiomyoma (2/3), leiomyosarcoma (3/3), sarcoma (NOS) (2/4), carcinosarcoma (1/1), malignant rhabdoid tumour (1/1), malignant Triton tumour (1/1), fibrous polyp (1/1), mesoblastic nephroma (1/1), hamartoma (1/1), and angiomyolipoma (1/1). Different tumour designations were suggested in 13 cases (13/31, 42%), including carcinosarcoma, sarcoma (NOS), leiomyosarcoma, solitary fibrous tumour, monomorphic/biphasic angiomyolipoma, endometrial stromal tumour, and congenital mesoblastic nephroma.

CONCLUSIONS

Our data indicate that although morphology is most important in formulating the initial differential diagnosis, the addition of immunohistochemistry is vital in arriving at the correct classification of RSCTs.

Solitary fibrous tumor of the kidney originating from the renal capsule and fed by the renal capsular artery

Solitary fibrous tumors (SFT) are relatively rare spindle cell neoplasms that typically arise in the pleura. Recently, extrathoracic SFT that have arisen in various anatomic sites have been recognized. The histogenesis and prognosis of SFT of the kidney are not well understood because only 11 cases have been reported. We report a case of SFT of the left kidney arising from the renal capsule. The tumor was merged with the upper pole of the left renal capsule. The angiography revealed that the renal capsule artery fed the tumor. The tumor was a well-circumscribed, solid mass attached to the renal capsule without necrosis or hemorrhage. Microscopically the bland spindle cells proliferated and were accompanied by hyalinized collagenous tissue showing patternless or hemangiopericytomatous patterns. Some glomeluri and renal tubules were entrapped by the tumor cells. There were no mitotic figures. Immunohistochemically the tumor cells were diffusely positive for CD34, CD99 and bcl-2. There was no evidence of recurrence after a 4 year follow-up visit. The origin of SFT of the kidney remains uncertain. The tumor in this case merged with the renal capsule and was fed by the renal capsular artery, which suggests that some SFT of the kidney originate from the renal capsule.

Handling and Pathology Reporting of Renal Tumor Specimens

The gold standard in the treatment of renal tumors is radical or partial nephrectomy. The surgical specimen handling is important since the pathologic features result in clinico-pathologic knowledge that determines prognosis, additional treatment and scientific studies. The correct handling of the specimen by urologists and pathologists becomes very basic in order to enable retrieval of a maximum of information. This protocol aims at standardization of the minimal criteria for handling, cellular subtyping, grading, staging and margin evaluation that must allow the comparison among the different scientific groups.

Mediastinal epithelioid solitary fibrous tumor

We describe the case of a 74-year-old man with a mediastinal tumor composed predominantly of epithelioid cells exhibiting histopathologic and immunohistochemical features intermediate between those of a solitary fibrous tumor and those of a cellular adenomatoid tumor. We discuss the differential diagnosis and possible histogenesis of this unusual neoplasm, and we propose the term epithelioid solitary fibrous tumor for this entity.