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

Hallmark discoveries in the biology of non-Wilms tumour childhood kidney cancers

Approximately 20% of paediatric and adolescent/young adult patients with renal tumours are diagnosed with non-Wilms tumour, a broad heterogeneous group of tumours that includes clear-cell sarcoma of the kidney, congenital mesoblastic nephroma, malignant rhabdoid tumour of the kidney, renal-cell carcinoma, renal medullary carcinoma and other rare histologies. The differential diagnosis of these tumours dates back many decades, when these pathologies were identified initially through clinicopathological observation of entities with outcomes that diverged from Wilms tumour, corroborated with immunohistochemistry and molecular cytogenetics and, subsequently, through next-generation sequencing. These advances enabled near-definitive recognition of different tumours and risk stratification of patients. In parallel, the generation of new renal-tumour models of some of these pathologies including cell lines, organoids, xenografts and genetically engineered mouse models improved our understanding of the development of these tumours and have facilitated the identification of new therapeutic targets. Despite these many achievements, paediatric and adolescent/young adult patients continue to die from such rare cancers at higher rates than patients with Wilms tumour. Thus, international coordinated efforts are needed to answer unresolved questions and improve outcomes.

Renal synovial sarcoma: Considerations for radical nephrectomy- a case report and literature review

Synovial sarcoma, a rare soft tissue malignancy typically arising from synovial tissue, primarily manifests in the extremities but it may uncommonly present in other locations such as kidneys. Primary renal synovial sarcoma is an uncommon sarcoma with high mortality and recurrence rates. Here, we present a teenage boy with primary renal synovial sarcoma who was referred to our institution.

Primary Ewing's Sarcoma of the Kidney Mimicking Renal Cell Carcinoma With Widespread Metastasis: A Case Report and a Brief Review of the Literature

Ewing's sarcoma family of tumors (ESFTs) are a group of small round cell tumors with common morphological and genetic features, including Ewing's sarcoma of bone, primary extra-skeletal Ewing tumors, extraosseous Ewing sarcoma (EES), and Askin tumors. EES presenting as a primary renal mass is an exceedingly uncommon aggressive tumor with limited reported cases in the literature and often mimics other renal malignancies on imaging. We present a case of a 31-year-old man presenting with left flank pain and abdominal fullness of short duration. Radiological imaging studies showed a large heterogenous mass from the left kidney, confirmed to be Ewing's sarcoma on post-operative histopathological examination (HPE) and immunohistochemistry (IHC) studies. Subsequent follow-up showed extensive metastatic disease. EES of the kidney has a nonspecific presentation and imaging appearance necessitating a multi-disciplinary approach comprising radiological imaging with a high index of suspicion, HPE, IHC, and molecular analysis for the correct diagnosis.

Primary Ewing sarcoma/primitive neuroectodermal tumors of the kidney: Case series of eight cases from a single center with follow-up details

Introduction

We aim to share the experience of a single center in the management of eight cases of renal primitive neuroectodermal tumor (PNET) which are uncommon, aggressive tumors. The objectives were to study the presentation of the disease, the treatment offered and its outcomes, and the comparison of the treatment with published literature.

Methods

The single-center renal PNET data of all patients were retrospectively reviewed from 2011 to 2022. Renal PNET was seen in eight patients. Minimum follow-up period of 1 year was required.

Results

Male-to-female ratio was 7:1. The mean age was 26.5 years. All were locally advanced tumors on presentation. One patient had an inferior vena cava thrombus, one patient had metastases on presentation, and two patients had tumor extending to paranephric space. The diagnosis was made by histopathology supported by immunohistochemistry showing CD99 positivity. All patients were treated with radical nephrectomy, followed by chemotherapy in all and radiotherapy in three patients. Two patients expired at 3½ and 6 years after surgery, the remaining six are alive at a median follow-up period of 34.5 months.

Conclusion

Renal PNET is an uncommon renal tumor which is aggressive and requires multimodal therapy for prolonged survival.

Epidemiology, treatment and outcomes of primary renal sarcomas in adult patients

To assess epidemiology, clinical presentation, treatment and overall survival of adult patients with renal sarcomas, the 2004-2016 SEER and NCDB databases were queried for adult patients diagnosed with renal sarcoma, calculating average annual age-adjusted incidence rates (AAIR) and average annual percentage change (AAPC) as well as overall survival (OS). In n = 1279 included renal sarcoma patients, AAIR remained constant over the study period (average 0.53 cases/1million; AAPC = 0.7, p = 0.6). Leiomyosarcoma (AAIR 0.14 cases/1 million) and malignant rhabdoid tumors (0.06 cases/1 million) were most common. Sarcoma histiotypes demonstrated considerable heterogeneity regarding demographic and cancer-related variables. Patients presented with advanced local extent (T3 33.3%; T4 14.2%) or distant metastases (29.1%) and commonly underwent surgical resection (81.6%). Longer OS was independently associated with younger age, female sex, lower comorbidity index, low T stage, negative surgical margins, absence of tumor necrosis or distant metastases and leiomyosarcoma histiotype (multivariable p < 0.05 each). Treatment efficacy varied according to sarcoma histiotype (interaction p < 0.001). Accounting for 0.25% of renal malignancies, renal sarcomas include 43 histiotypes with distinct epidemiology, clinical presentation, outcomes and sensitivity to systemic therapy, thereby reflecting soft-tissue sarcoma behavior. Renal sarcoma treatment patterns follow recommendations by renal cancer guidelines with surgical resection as the cornerstone of therapy.

Soft-Tissue Sarcomas of the Genitourinary Tract with Radiologic-Pathologic Correlation

Genitourinary tract soft-tissue sarcomas are rare neoplasms with varied pathologic and clinical features. While some of these tumors may be aggressive high-grade malignancies, others are low grade with a relatively better prognosis. Given that the grade and extent of the disease are important prognostic factors in these tumors, timely diagnosis is crucial. Unfortunately, most imaging features of these malignancies are not pathognomonic, and various histologic subtypes do not manifest with typical classic imaging features. Therefore, reliable differentiation of the various histologic tumor types is not always possible based solely on the radiologic manifestations. Imaging findings need to be considered in the context of clinical history in corroboration with radiologic-pathologic correlation. The authors discuss the specific imaging and pathologic characteristics of various genitourinary tract soft-tissue sarcomas, emphasizing diagnostic difficulties and differential diagnoses. ©RSNA, 2024 Test Your Knowledge questions for this article are available in the supplemental material.

Primary Ewing’s sarcoma of the kidney: a rare masquerader of renal cell carcinoma on imaging

Background

The Ewing sarcoma family of tumors comprises a group of high-grade small round cell tumors, including Ewing sarcoma of bone, extra-skeletal Ewing sarcoma, peripheral primitive neuro-ectodermal tumor (PNET), and Askin tumor (thoraco-pulmonary PNET). They are more prevalent in young children and adolescents. Ewing's Sarcoma is an aggressive tumor majorly described in bones. Primary renal Ewing's sarcoma is an extremely rare entity, characterized by a very aggressive course, with very few reported cases in the literature.

Case presentation

We present an 18-year-old girl who presented with sudden onset left flank pain and hematuria. The patient had histopathology-proven primary renal Ewing's sarcoma, which was initially misdiagnosed as renal cell carcinoma on imaging.

Conclusions

Owing to its non-specific radiological appearance, a high index of suspicion and a systematic approach is essential for detection of renal Ewing’s Sarcoma.

Extraosseous Ewing's sarcoma/peripheral primitive neuroectodermal tumour of the kidney: a case report and literature review

BACKGROUND

Extraosseous Ewing's sarcoma/peripheral primitive neuroectodermal tumours(EWS/pPNETs) of the kidney are rare. Signs and symptoms are atypical in EWS patients. Presenting symptoms include haematuria, abdominal pain, or a palpable mass. A comprehensive review of the literature shows that it is difficult to make an accurate diagnosis based on physical examination alone. The imaging findings of EWS/pPNETs are nonspecific. We used contrast-enhanced ultrasound (CEUS) to diagnose an EWS/pPNET in our patient, which had never been reported previously to our knowledge.

CASE PRESENTATION

This article reports the case of a 20-year-old female with an abdominal mass and gross haematuria for 1 month. The ultrasound revealed a hypoechoic mass with a clear margin at the lower pole in the left kidney. CEUS demonstrated signs of annular enhancement and heterogeneous enhancement of the tumour, and simultaneous wash-in was predominant. Computed tomography images showed an elliptical low-density tumour. The patient underwent a left kidney resection, and the pathological diagnosis was an EWS/pPNET. Twenty-one days after the kidney operation, the patient underwent 8 cycles of a CAV (vinorelbine, ifosfamide, epirubicin) + IE (isocyclophosphamide, etoposide) chemotherapy regimen. Subsequently, radiotherapy (dose: 45 Gy, radiation field:the tumour bed following surgical resection) was administered for nearly 30 days. The patient had no signs of local recurrence or metastasis within a follow-up of 4 years.

CONCLUSIONS

As a radiation-free, inexpensive, convenient, and repeatable examination method, ultrasound was the primary choice for kidney examination. Early CEUS was helpful to make an accurate diagnosis. Surgery and adjuvant radiation or chemotherapy administered in a timely manner can prevent further deterioration.

Primary renal sarcomas: imaging features and discrimination from non-sarcoma renal tumors

OBJECTIVES

To assess imaging features of primary renal sarcomas in order to better discriminate them from non-sarcoma renal tumors.

METHODS

Adult patients diagnosed with renal sarcomas from 1995 to 2018 were included from 11 European tertiary referral centers (Germany, Belgium, Turkey). Renal sarcomas were 1:4 compared to patients with non-sarcoma renal tumors. CT/MRI findings were assessed using 21 predefined imaging features. A random forest model was trained to predict "renal sarcoma vs. non-sarcoma renal tumors" based on demographics and imaging features.

RESULTS

n = 34 renal sarcomas were included and compared to n = 136 non-sarcoma renal tumors. Renal sarcomas manifested in younger patients (median 55 vs. 67 years, p < 0.01) and were more complex (high RENAL score complexity 79.4% vs. 25.7%, p < 0.01). Renal sarcomas were larger (median diameter 108 vs. 43 mm, p < 0.01) with irregular shape and ill-defined margins, and more frequently demonstrated invasion of the renal vein or inferior vena cava, tumor necrosis, direct invasion of adjacent organs, and contact to renal artery or vein, compared to non-sarcoma renal tumors (p < 0.05, each). The random forest algorithm yielded a median AUC = 93.8% to predict renal sarcoma histology, with sensitivity, specificity, and positive predictive value of 90.4%, 76.5%, and 93.9%, respectively. Tumor diameter and RENAL score were the most relevant imaging features for renal sarcoma identification.

CONCLUSION

Renal sarcomas are rare tumors commonly manifesting as large masses in young patients. A random forest model using demographics and imaging features shows good diagnostic accuracy for discrimination of renal sarcomas from non-sarcoma renal tumors, which might aid in clinical decision-making.

KEY POINTS

• Renal sarcomas commonly manifest in younger patients as large, complex renal masses. • Compared to non-sarcoma renal tumors, renal sarcomas more frequently demonstrated invasion of the renal vein or inferior vena cava, tumor necrosis, direct invasion of adjacent organs, and contact to renal artery or vein. • Using demographics and standardized imaging features, a random forest showed excellent diagnostic performance for discrimination of sarcoma vs. non-sarcoma renal tumors (AUC = 93.8%, sensitivity = 90.4%, specificity = 76.5%, and PPV = 93.9%).

Primary Renal Synovial Sarcoma and Clinical and Pathological Findings: a Systematic Review

PURPOSE OF REVIEW

To update epidemiological, diagnostic, and therapeutic information on primary synovial sarcoma of the kidney.

RECENT FINDINGS

A total of 96 studies were analyzed; age at presentation was 38.6±14.2 years, predominant location of tumor was right kidney; frequent reported symptoms at diagnosis were hematuria and pain. For definitive diagnosis, cytogenetic technique was used. Detected oncogene was available in 37.8% cases with fusion of SS18-SSX in most patients. Surgery is treatment of choice, with adjuvant chemotherapy; most frequently ifosfamide-based associated with doxorubicin or epirubicin. Overall median survival was 34 months. Mortality was 29% of the cases which reported death and the recurrence rate was 39.8%. Risk of death was increased in patients with metastases at diagnosis Primary RSS occurs more often in young men. RSS often presents with symptoms and in an advanced stage. Surgical treatment is the most commonly used and chemotherapy for advanced or recurrent treatment.

[A CASE OF RENAL UNDIFFERENTIATED/UNCLASSIFIED SARCOMA WITH LONG-TERM SURVIVAL AFTER PRIMARY AND METASTATIC LESIONS]

(Case) A 56-year-old woman who complained of urinary frequency and macrohematuria. Abdominal US, enhanced CT and MRI revealed a left renal tumor. A left radical nephrectomy was performed in May 1997, and the pathological diagnosis was renal fibrosarcoma. Follow-up computed CT was performed routinely. A metastatic lesion in the right lung revealed 19 months after the nephrectomy.She underwent partial pneumonectomy in January 1999, and the pathological diagnosis was also fibrosarcoma. She was followed up until 2009 without recurrence.In 2015, she was admitted in the Department of Orthopedics due to femoral neck fracture in 2015, thus we could find out she was alive, tumor-free 18 years after the nephrectomy. We added the immunohistochemistical study to her specimen of kidney and lung, and the diagnosis was changed to undifferentiated/unclassified sarcoma. (Conclusion) Metastatic renal sarcoma has a poor prognosis in general. We experienced a long-term survival case of undifferentiated/unclassified renal sarcoma with lung metastasis, and report it with some literature review.

Primary renal embryonal rhabdomyosarcoma in an adult patient

Adult renal rhabdomyosarcoma (RMS) is a rare and aggressive entity with a paucity of data and reports in the literature. As a result, treatment guidelines for this malignancy are not well-established. Herein, we present the diagnosis, management and clinical course of a 39-year-old patient diagnosed with primary renal embryonal RMS (ERMS) following radical nephrectomy. We also review the existing literature on primary renal ERMS.

Multimodality-imaging manifestations of primary renal-allograft synovial sarcoma: First case report and literature review

BACKGROUND

Primary renal synovial sarcoma (PRSS) is an extremely rare tumor with a poor prognosis. Its imaging and immunohistochemical characteristics may overlap with other renal tumors, which renders its early diagnosis in a dilemma. The diagnosis of primary renal synovial sarcoma requires histopathology and the confirmation of SYT-SSX gene fusion using molecular techniques. Cases of primary renal synovial sarcoma have been previously reported in the literature. However, to our knowledge, primary renal allograft synovial sarcoma was never described.

CASE SUMMARY

A 43-year-old male patient who underwent kidney transplantation 9 months ago came to our hospital for regular follow-up. Traditional ultrasonography revealed multiple hypo-echo neoplasms in the renal allograft. Contrast-enhanced computed tomography (CECT) showed slightly hyper-density masses with slow homogeneous enhancement. Ultrasound-guided biopsy was conducted for accurate pathological diagnosis. The neoplasms were diagnosed as synovial sarcoma by pathological, immunohistochemical, and genetic analyses. Positron emission tomography/CT showed no evidence of metastasis. At approximately one week post biopsy, contrast-enhanced ultrasound was conducted to eliminate active hemorrhage. One month later, CECT showed that the biggest neoplasm grew from 3.3 cm to 5.7 cm in diameter. Parametric imaging was conducted with SonoLiver CAP to conduct further quantitative analysis, which showed that the enhancement pattern was heterogeneous hyper-vascular enhancement. Radical surgical resection of the whole renal allograft and ureter was conducted without additional adjuvant chemotherapy or external radiotherapy. Anlotinib was chosen for targeted therapy with a good response.

CONCLUSION

We propose multimodality imaging for accurate diagnosis of renal allograft synovial sarcoma especially when it is formed by spindle-shaped cells.

Magnetic resonance imaging (MRI) of the renal sinus

This article presents methods to improve MR imaging approach of disorders of the renal sinus which are relatively uncommon and can be technically challenging. Multi-planar Single-shot T2-weighted (T2W) Fast Spin-Echo sequences are recommended to optimally assess anatomic relations of disease. Multi-planar 3D-T1W Gradient Recalled Echo imaging before and after Gadolinium administration depicts the presence and type of enhancement and relation to arterial, venous, and collecting system structures. To improve urographic phase MRI, concentrated Gadolinium in the collecting systems should be diluted. Diffusion-Weighted Imaging (DWI) should be performed before Gadolinium administration to minimize T2* effects. Renal sinus cysts are common but can occasionally be confused for dilated collecting system or calyceal diverticula, with the latter communicating with the collecting system and filling on urographic phase imaging. Vascular lesions (e.g., aneurysm, fistulas) may mimic cystic (or solid) lesions on non-enhanced MRI but can be suspected by noting similar signal intensity to the blood pool and diagnosis can be confirmed with MR angiogram/venogram. Multilocular cystic nephroma commonly extends to the renal sinus, however, to date are indistinguishable from cystic renal cell carcinoma (RCC). Solid hilar tumors are most commonly RCC and urothelial cell carcinoma (UCC). Hilar RCC are heterogeneous, hypervascular with epicenter in the renal cortex compared to UCC which are centered in the collecting system, homogeneously hypovascular, and show profound restricted diffusion. Diagnosis of renal sinus invasion in RCC is critically important as it is the most common imaging cause of pre-operative under-staging of disease. Fat is a normal component of the renal sinus; however, amount of sinus fat correlates with cardiovascular disease and is also seen in lipomatosis. Fat-containing hilar lesions include lipomas, angiomyolipomas, and less commonly other tumors which engulf sinus fat. Mesenchymal hilar tumors are rare. MR imaging diagnosis is generally not possible, although anatomic relations should be described to guide diagnosis by percutaneous biopsy or surgery.

Biphasic renal synovial sarcoma with extensive venous tumor thrombosis: A rare presentation

Primary renal synovial sarcoma (SS) is a very rare soft-tissue tumor arising from the kidney. These tumors histologically closely resemble other sarcoma variants. Immunohistochemical and cytogenetic techniques remain the cornerstone in achieving the correct diagnosis. Radical surgical excision is the primary treatment for local tumor control and alleviation of symptoms. Adjuvant chemotherapy, at present, has only a limited role. We report a unique case of a 21-year-old young male with the diagnosis of a biphasic renal SS with extensive venous system thrombosis involving the inferior vena cava, bilateral iliac, and femoral vessels which was managed by radical nephrectomy and tumor thrombectomy followed by adjuvant chemotherapy.

Primitive neuroectodermal tumors of the kidney

Ewing's sarcoma/primitive neuroectodermal tumor (ES/PNET) rarely occurs as a primary renal tumor. The disease affects young adults and children and has an aggressive course. The clinical presentation and imaging of these tumors are nonspecific, and they often present at an advanced stage. We present the clinical features, imaging, diagnosis, and treatment of 7 cases of renal PNET (4 men, 3 women; median age, 32 years). Common presenting symptoms were flank or abdominal pain and a mass in the abdomen. On imaging, a large heterogenous infiltrating renal mass with areas of calcification, hemorrhage, and necrosis and tumor thrombus can give a clue to the diagnosis of renal PNET. Immunohistochemistry and molecular studies are essential to confirm the diagnosis. The prognosis of renal ES/PNET is generally poor. Radical nephrectomy combined with chemotherapy and radiotherapy is the standard treatment for renal PNET. An early and accurate diagnosis is crucial for the proper management of these aggressive tumors.

Renal Synovial Sarcoma in a Young Pregnant Lady: A Case Report and Clinico-Pathological Profile

Synovial sarcoma is a soft tissue neoplasm with clearly defined histologic, immunohistochemical and molecular features. These tumours usually arise in the extremities of young adults. Their occurrence in the kidney is extremely rare. A 25-year-old pregnant lady in her first trimester was incidentally found to have a left renal mass on perinatal ultrasonography. MRI showed a well encapsulated, heterointense mass replacing the left kidney. Following medical termination of her pregnancy, a radical nephrectomy was performed. Histopathology revealed a primary synovial cell sarcoma of the kidney. Postoperatively, she received ifosfamide based adjuvant chemotherapy. This report highlights the challenges involved in the diagnosis of this extremely rare neoplasm. A high index of clinical suspicion, complimented by the use of immunohistochemistry and cytogenetics during histopathological analysis aide in the diagnosis. Aggressive management with a combination of complete surgical extirpation and chemotherapy gives the best results.

Renal Tumors of Childhood: Radiologic-Pathologic Correlation Part 1. The 1st Decade: From the Radiologic Pathology Archives

Wilms tumor is the second most common pediatric solid tumor and by far the most common renal tumor of infants and young children. As most tumors are large at presentation and are treated with nephrectomy, the role of imaging is primarily in preoperative planning and evaluation for metastatic disease. However, with treatment protocols increasingly involving use of preoperative (neoadjuvant) chemotherapy (the standard in Europe) and consideration of nephron-sparing surgery, the role of imaging is evolving to include providing initial disease staging information and a presumptive diagnosis to guide therapy. Differential diagnostic considerations include lesions that are clinically benign and others that require more intensive therapy than is used to treat Wilms tumor. In part 1 of this article, the unique histologic spectrum of renal neoplasms of infants and young children is reviewed with emphasis on radiologic-pathologic correlation. Part 2 will focus on renal tumors of older children and adolescents.

CT Features and Pathological Correlation of Primitive Neuroectodermal Tumor of the Kidney

The purpose of the study was to analyze the computed tomography (CT) findings of primitive neuroectodermal tumor (PNET) of the kidney and correlate them pathologically. Ten cases of pathologically confirmed renal PNET were collected and retrospectively reviewed. The CT features that were analyzed include tumor size, shape, margins, density, nature of enhancement, presence of thrombosis, and metastasis, etc. These parameters were correlated with pathological findings and combined with literature review. The median age of the patients was 30 years. CT images showed solitary, large, ill-defined, irregular, or lobulated heterogeneous mass. Invasive growth toward the renal cortex and pelvis with renal cortical interruptions were seen in eight cases with one case exhibiting invasion that extended beyond the renal capsule with soft tissue seen in the perirenal fat pace. The tumors were confined to the kidney contour with enlargement of kidney in six of the cases. Cystic changes with mural nodules were detected in three cases. Eight cases showed persistent moderate enhancement during the nephrographic phase. Irregular septum-like structures were seen in four cases. Thrombosis was detected in eight cases. Lymph node metastasis was detected in eight cases with bilateral lung metastasis in two and bone metastasis in one. Renal PNET is a rare highly aggressive disease affecting younger people. It should be considered as a strong differential when well confined, yet large tumors that cause enlargement of the kidney are seen and also when tumors expressing cystic changes along with mural nodules are seen. Although renal PNET has certain other characteristic CT features, pathological and immunohistochemistry report must also be sought for definitive diagnosis.

Rare neoplasm of genito-urinary tract. Genito-urinary sarcomas: chemotherapy

PURPOSE OF REVIEW

The purpose of this article was to describe the systemic therapy of genito-urinary sarcomas.

RECENT FINDINGS

High rate of distant metastasis and high mortality rate has brought interest into the development of new therapeutic approaches. Various modules of chemotherapy were sampled in sarcoma treatment, although clinical response is still unsatisfactory. Chemotherapy in sarcomas can be used as neoadjuvant or adjuvant to the surgery. There is no consensus on the current role of adjuvant chemotherapy. Study results are conflicting; therefore, conclusions drawn from the studies are uncertain. In general, the adjuvant chemotherapy is not standard treatment in adult-type sarcomas. In addition, chemotherapy for advanced and metastatic sarcoma disease, as well as second-line chemotherapy, was discussed.

SUMMARY

The best treatment for sarcomas in case of organ-confined disease and in selected cases of locally advanced disease seems to be surgery followed by chemotherapy. In case of metastasis stage of sarcoma, preoperative chemotherapy with surgery of residual masses should be considered as first-line treatment followed by postoperative chemotherapy. The treatment of patient with highly advanced disease and/or unresectable metastases should be individualized (chemotherapy, radiotherapy and best supportive care).

CT and MRI Findings in a Rare Case of Renal Primitive Neuroectodermal Tumor

BACKGROUND

Primary renal primitive neuroectodermal tumor/extraskeletal Ewing's sarcoma (PNET/EES) is a very rare renal tumor.

CASE REPORT

We report a case of primary renal PNET/EES of the kidney in an adult patient and describe its computed tomography and magnetic resonance imaging findings, including diffusion weighted images along with a review of the current medical literature.

CONCLUSIONS

Although very rare, a relatively large renal mass which shows very infiltrative growth pattern on CT and MR imaging and striking diffusion restriction should raise the suspicion of a renal primitive neuroectodermal tumor, in a young adult.

Unusual Malignant Solid Neoplasms of the Kidney: Cross-Sectional Imaging Findings

Malignant kidney neoplasms are the most frequently encountered solid kidney masses. Although renal cell carcinoma is the major renal malignancy, other solid malignant renal masses should be considered in the differential diagnosis of solid renal masses that do not contain a macroscopic fatty component. In this pictorial essay, we present the imaging findings of a primitive neuroectodermal tumor, primary liposarcoma of the kidney, primary neuroendocrine tumor, leiomyosarcoma, synovial sarcoma, malignant fibrous histiocytoma, sclerosing fibrosarcoma and renal metastasis of osteosarcoma.

Primary renal synovial sarcoma: computed tomography imaging findings

BACKGROUND

A synovial sarcoma arising from the kidney is extremely rare. To date, few data are available on their radiological features.

PURPOSE

To identify the computer tomography (CT) imaging findings of primary renal synovial sarcomas (PRSSs).

MATERIAL AND METHODS

Five cases of PRSS confirmed by histopathological and cytogenetic studies were retrospectively analyzed. All patients had undergone unenhanced and multiphase enhanced CT examinations (one patient underwent CT twice). The CT characteristics, including shape, size, margin, attenuation, and enhancement pattern after intravenous contrast medium injection, were analyzed.

RESULTS

The study involved two female and three male patients (mean age, 27.4 years; range, 15-43 years). Unenhanced CT showed completely or partly well-defined masses, with heterogeneous (n = 5) or homogeneous (n = 1) patchy low density. On multiphase contrast-enhanced CT, in five of the six CT examinations, the tumors appeared as solid-cystic masses with cyst walls or pseudo-capsules, and demonstrated moderately heterogeneous (n = 5) and/or septate enhancement (n = 2), with a "rapid wash-in and slow wash-out" pattern of enhancement in the solid component. Only one tumor showed a simple cyst appearance and developed an irregular, intratumoral, septate soft density 8 months later. A renal vein and inferior vena cava thrombus was noticed in one patient, while lymphadenopathy was not observed in any patient.

CONCLUSION

PRSS should be included in the differential diagnosis when an adolescent or young adult presents with a renal neoplasm appearing as a solid-cystic mass with well-defined borders, a cystic wall or pseudo-capsule, heterogeneous or septate enhancement, a "rapid wash-in and slow wash-out" pattern of enhancement in the solid component, and no sign of lymphadenopathy.

Peripheral neuroectodermal tumour of the kidney (Ewing's sarcoma): Restaging with (18)F-fluorodeoxyglucose (FDG)-PET/CT

Primitive peripheral neuroectodermal tumour and Ewing's sarcoma (PNET/EWS) were originally described as two distinct pathologic entities, although both share common stem-cell precursor and unique chromosomal abnormality. Although its incidence has increased recently, its share in all sarcomas is 1%. It is usually seen in men and women in their twenties. We present a case of a 38-year-old woman with a left renal mass detected incidentally. Magnetic resonance imaging revealed a centrally located hypervascular renal mass with diameter of 6 cm with non-homogenous contrast enhancement containing necrotic and calcific areas. The patient was diagnosed as having PNET/EWS by histopathological examination following radical nephrectomy. Para-aortic lymph node metastasis was found on imaging by (18)F-fluorodeoxyglucose (FDG)-positron-emission tomography/computed tomography (PET/CT).

Prognostic features of renal sarcomas (Review)

The aim of the present review was to evaluate the prognostic features of primary sarcomas of the kidney. A literature review was conducted using a number of databases, including Medline (PubMed) and Scopus, for studies published between January 1992 and December 2013. Of the studies published in English, those describing the prognostic features of primary sarcomas of the kidney were recorded. The electronic search was limited to the following keywords: Sarcoma, renal sarcoma, prognosis, diagnosis, immunohistochemistry, genetic and survey. Subsequent to the search, no review articles and/or meta-analyses associated with the prognosis of primary sarcomas of the kidney were identified. In total, 31 studies, which consisted of case studies, case series and studies concerned with the overall prognosis of urological soft-tissue sarcomas, were reviewed. Primary sarcoma of the kidney has a poor prognosis compared with other sarcomas of the urogenital system. In addition to the surgical excision of renal sarcomas, pathological, molecular and genetic prognostic factors are also considered. Due to the small number of cases, previous studies have not randomized the prognostic features of primary sarcomas of the kidney. The elucidation of the so-called ‘chaotic’ genetic and molecular basis of renal sarcomas will help to predict patient prognoses. Surgical excision is the most significant parameter for determining the prognosis of sarcomas of the kidney. However, sarcomas also exhibit prognostic features that are based upon pathological, genetic and molecular factors. The present review suggests that additional factors may be important in predicting the prognosis of patients with renal sarcomas, and that clinicians should plan treatment and follow-up regimens according to these factors.

Ewing sarcoma of the kidney: a rare entity

Ewing sarcoma and primitive peripheral neuroectodermal tumor (PNET) are high-grade malignant tumors typically found in children and adolescents. These tumors belong to the family of small round cell tumors and are of neuroectodermal origin. Primary Ewing sarcoma of the kidney is rare and because of that is an infrequent differential diagnosis in urologic malignancies. Renal PNET mostly presents with nonspecific symptoms such as hematuria and abdominal pain. The imaging findings are uncharacteristic. The diagnosis is based on the histology, immunohistochemistry, and molecular pathologic findings. Once PNET has been diagnosed, multimodal treatment is indicated. Despite all treatment options, the prognosis of those with metastatic disease is poor.

Primary renal embryonal rhabdomyosarcoma in adults: a case report and review of the literature

Adult renal rhabdomyosarcoma is a rare subtype of renal sarcoma. We present a case of a renal mass treated with radical nephrectomy that subsequently was shown to be renal rhabdomyosarcoma. We discuss the clinical presentation, imaging findings, and histology for this case and review the available literature.

Clinical and pathological features of primary renal synovial sarcoma: analysis of 64 cases from 11 years of medical literature

OBJECTIVE

To describe, for the first time, the clinical characteristics of primary renal synovial sarcoma (SS) and to examine the association of histological features with the expression of immunohistochemical markers.

PATIENTS AND METHODS

We collated published data on all cases of primary renal SS, from its first description in 2000 to September 2011. Data on clinical and pathological characteristics were extracted and used to create a database. Disease-free survival (DFS) and overall survival (OS) rates were estimated using the Kaplan-Meier method with Rothman's 95% confidence intervals (CIs) and compared across the groups using the log-rank test. The associations between tumour extension and histological features were evaluated using the non-parametric Spearman rank test. A chi-squared test was used to assess the differences between groups.

RESULTS

In the overall cohort, the median OS was 48 months (95% CI, 14.1-81.9). Cox analysis showed that the risk of death at diagnosis was greatly increased in patients with metastatic disease compared with those with non-metastatic disease (hazard ratio [HR]: 343.9, 95% CI, 2.8-42,000; P= 0.017). The median DFS was 33.0 months (95% CI, 16.8-49.2), and patients who develop metastatic disease have a very poor prognosis with a median survival of 6 months (95% CI, 5.1-6.9). Microscopic features were monophasic, biphasic and poorly differentiated synovial sarcoma in 76, 16 and 8% of patients, respectively. Significant differences in expression of immunohistochemical markers or genetic mutation were found between different subtypes.

CONCLUSIONS

Despite its retrospective nature, this study shows that renal SS comprises different histological subtypes, which are characterized by specific immunohistochemical stains and by specific translocations. When diagnosed at metastatic stage, the prognosis was very poor compared with that for non-metastatic disease, even though one out of three patients with non-metastatic disease had disease relapse. Cooperative efforts and publication of cases with adequate follow-up are necessary to better define prognosis and therapeutic strategies for this rare disease.