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Most pediatric specialists, including hematologists/oncologists, surgeons, radiologists, and pathologists, are familiar with the diagnosis and management of Wilms tumor (WT). However, it may be challenging to identify the underlying conditions causing cancer predisposition, which can change the management for the patient and potentially their entire family. In this paper, we present 3 cases of clinically suspected WT associated with Beckwith-Wiedemann syndrome (BWS). We review the radiologic and histologic findings to diagnose BWS. We also discuss the implications of a BWS diagnosis on the clinical management of WT and follow-up guidelines for BWS patients., Competing Interests: The authors declare no conflict of interest., (Copyright © 2024 The Author(s). Published by Wolters Kluwer Health, Inc.)

Background and Aims: Tumour rupture (TR) signifies stage III disease and requires treatment intensification, which includes radiotherapy. We studied the associations between radiological, surgical and pathology TR in children with Wilms tumour (WT) in a United Kingdom multicentre clinical study., Patients and Methods: The IMPORT (Improving Population Outcomes for Renal Tumours of Childhood) study registered 712 patients between 2012 and 2021. Children with TR on central radiology review (CRR) at diagnosis and/or indication of preoperative TR on surgical forms were included. Correlation between radiology/surgery/pathology findings was made., Results: Total 141 patients had TR identified (69 on CRR, 43 on surgical form and 29 on both), and 124/141 had images available for CRR, and 98/124 had features suggestive of TR on diagnostic CRR (63 magnetic resonance imaging/35 computed tomography). TR was limited to the renal fossa in 47/98 (48%) and intraperitoneal in 51/98 (52%). Three of 98(3%) had upfront surgery, and 87/95 (92%) had TR confirmed on post-chemotherapy preoperative scans. Among 80/98 (82%) cases with TR on CRR and available surgical forms, TR was not confirmed on surgery or pathology in 38/80, giving a false-positive rate of 48%. Preoperative TR was indicated on 72 surgical forms, with images available for CRR in 55. Twenty-six of 55 (47%) were false-negative for TR on CRR and of those 10/26 (38%) had TR confirmed on pathology., Conclusions: Radiology alone should not be used to define TR, as it does not accurately correlate with surgical or pathology findings, and therefore cannot be relied upon for definitive staging and treatment. A multidisciplinary team should take the decision regarding the final abdominal stage and treatment using a multimodality approach considering clinical, radiological, surgical and pathological findings., (© 2024 The Author(s). Pediatric Blood & Cancer published by Wiley Periodicals LLC.)

Background: Horseshoe kidney is the most common renal fusion anomaly, and Wilms tumor is the most frequent renal malignancy in children. The occurrence of Wilms tumor in association with horseshoe kidney is a scarce anomaly. However, the arising of a teratoid type, which is a rare variant of Wilms tumor in a horseshoe kidney, is exceptionally unique., Case Presentation: This report presents a 5-year-old male admitted with horseshoe kidney involved by a large heterogeneous calcified mass that was diagnose on biopsy as Wilms tumor blastemal dominant. According to the local and regional extension and metastatic tumor in the lungs, the patient underwent neoadjuvant chemotherapy and then surgery. Post-operative pathologic findings confirmed the diagnosis of teratoid Wilms tumor., Conclusions: The occurrence of renal anomalies associated with a malignancy might be more frequent in the clinical environment. There are numerous differential diagnoses for renal tumors and masses, but the possibility of exceptional anomalies should not be denied, and clinicians should be prepared for these occasions. Although studies propose that chemotherapy has a trivial effect on teratoid Wilms tumors, it is essential to evaluate the tumor for any possibility of regression in non-teratoid regions before proceeding to upfront tumoral resection., (© 2024. The Author(s).)

Background: Wilms' tumor is the most common renal tumor in children., Objective: To correlate the percentage of necrosis and tumor volume change found in preoperative Contrast Enhance Computed Tomography (CECT) scan of the abdomen with post-operative histopathological findings of Wilms Tumor (WT)., Methods: In this prospective study from January 2020 to December 2022, out of 33 patients, 15 patients with unilateral localized WT (stage I, II, and III) treated according to SIOP UMBRELLA protocol 2016 were included. Bilateral, syndromic, and stage IV WT were excluded. The radiological response was measured in preoperative CECT by estimating the percentage of necrosis found in static images and compared with post-operative histopathological findings. Tumor volume changes were measured by comparing CECT at diagnosis and following chemotherapy. Tumor volume change was also compared with histology., Results: There was a significant positive correlation between radiological response to necrosis with histology as per Pearson correlation. Significant positive correlation also found between volume changes on pre and post chemotherapy CECT with histology as per Spearman correlation., Conclusions: The changes in tumors during preoperative radiological evaluation and histologically confirmed necrosis are strongly related., Competing Interests: Conflicts of interest There are no conflicts of interest., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Objectives: Machine learning methods can be applied successfully to various medical imaging tasks. Our aim with this study was to build a robust classifier using radiomics and clinical data for preoperative diagnosis of Wilms tumor (WT) or neuroblastoma (NB) in pediatric abdominal CT., Material and Methods: This is a single-center retrospective study approved by the Institutional Ethical Board. CT scans of consecutive patients diagnosed with WT or NB admitted to our hospital from January 2005 to December 2021 were evaluated. Three distinct datasets based on clinical centers and CT machines were curated. Robust, non-redundant, high variance, and relevant radiomics features were selected using data science methods. Clinically relevant variables were integrated into the final model. Dice score for similarity of tumor ROI, Cohen's kappa for interobserver agreement among observers, and AUC for model selection were used., Results: A total of 147 patients, including 90 WT (mean age 34.78 SD: 22.06 months; 43 male) and 57 NB (mean age 23.77 SD:22.56 months; 31 male), were analyzed. After binarization at 24 months cut-off, there was no statistically significant difference between the two groups for age (p = .07) and gender (p = .54). CT clinic radiomics combined model achieved an F1 score of 0.94, 0.93 accuracy, and an AUC 0.96., Conclusion: In conclusion, the CT-based clinic-radiologic-radiomics combined model could noninvasively predict WT or NB preoperatively. Notably, that model correctly predicted two patients, which none of the radiologists could correctly predict. This model may serve as a noninvasive preoperative predictor of NB/WT differentiation in CT, which should be further validated in large prospective models., Clinical Relevance Statement: CT-based clinic-radiologic-radiomics combined model could noninvasively predict Wilms tumor or neuroblastoma preoperatively., Key Points: • CT radiomics features can predict Wilms tumor or neuroblastoma from abdominal CT preoperatively. • Integrating clinic variables may further improve the performance of the model. • The performance of the combined model is equal to or greater than human readers, depending on the lesion size., (© 2024. The Author(s).)

Background: 3D reconstruction of Wilms' tumor provides several advantages but are not systematically performed because manual segmentation is extremely time-consuming. The objective of our study was to develop an artificial intelligence tool to automate the segmentation of tumors and kidneys in children., Methods: A manual segmentation was carried out by two experts on 14 CT scans. Then, the segmentation of Wilms' tumor and neoplastic kidney was automatically performed using the CNN U-Net and the same CNN U-Net trained according to the OV 2 ASSION method. The time saving for the expert was estimated depending on the number of sections automatically segmented., Results: When segmentations were performed manually by two experts, the inter-individual variability resulted in a Dice index of 0.95 for tumor and 0.87 for kidney. Fully automatic segmentation with the CNN U-Net yielded a poor Dice index of 0.69 for Wilms' tumor and 0.27 for kidney. With the OV 2 ASSION method, the Dice index varied depending on the number of manually segmented sections. For the segmentation of the Wilms' tumor and neoplastic kidney, it varied respectively from 0.97 to 0.94 for a gap of 1 (2 out of 3 sections performed manually) to 0.94 and 0.86 for a gap of 10 (1 section out of 6 performed manually)., Conclusion: Fully automated segmentation remains a challenge in the field of medical image processing. Although it is possible to use already developed neural networks, such as U-Net, we found that the results obtained were not satisfactory for segmentation of neoplastic kidneys or Wilms' tumors in children. We developed an innovative CNN U-Net training method that makes it possible to segment the kidney and its tumor with the same precision as an expert while reducing their intervention time by 80%., (© 2024. The Author(s).)

Background: Radiologic volumetric evaluation of Wilms' tumor (WT) is an important indicator to guide treatment decisions. However, due to the heterogeneity of the tumors, radiologists have main-guard differences in diagnosis that can lead to misdiagnosis and poor treatment. The aim of this study was to explore whether CT-based outlining of WT foci can be automated using deep learning., Methods: We included CT intravenous phase images of 105 patients with WT and double-blind outlining of lesions by two radiologists. Then, we trained an automatic segmentation model using nnUnet. The Dice similarity coefficient (DSC) and 95th percentile Hausdorff distance (HD 95 ) were used to assess the performance. Next, we optimized the automatic segmentation results based on the ratio of the three-dimensional diameter of the lesion to improve the performance of volumetric assessment., Results: The DSC and HD 95 was 0.83 ± 0.22 and 10.50 ± 8.98 mm. The absolute difference and percentage difference in tumor size was 72.27 ± 134.84 cm 3 and 21.08% ± 30.46%. After optimization according to our method, it decreased to 40.22 ± 96.06 cm 3 and 10.16% ± 9.70%., Conclusion: We introduce a novel method that enhances the accuracy of predicting WT volume by integrating AI automated outlining and 3D tumor diameters. This approach surpasses the accuracy of using AI outcomes alone and has the potential to enhance the clinical evaluation of pediatric patients with WT. By intertwining AI outcomes with clinical data, this method becomes more interpretive and offers promising applications beyond Wilms tumor, extending to other pediatric diseases., (© 2024. The Author(s).)

Bilateral Wilms tumour (BWT) is a surgically challenging condition. Virtual reality (VR) reconstruction aids surgeons to foresee the anatomy ahead of Nephron Sparing Surgery (NSS). Three-dimensional (3D) visualisation improves the anatomical orientation of surgeons performing NSS. We herewith report a case of BWT where VR planning and 3D printing were used to aid NSS. Conventional imaging is often found to be inadequate while assessing the tumour-organ-vascular anatomy. Advances like VR and 3D printing help surgeons plan better for complex surgeries like bilateral NSS. Next-generation extended reality tools will likely aid robotic-assisted precision NSS and improve patient outcomes., Competing Interests: Competing interests: None declared., (© BMJ Publishing Group Limited 2024. No commercial re-use. See rights and permissions. Published by BMJ.)

Abstract: Congenital mesoblastic nephroma is an extremely rare, low-grade malignant renal tumor in children. A 10-month-old boy and a 4-month-old girl were admitted to our hospital with a huge abdominal mass. For staging of the mass, 18 F-FDG PET/CT and PET/MR were performed showing a huge heterogeneous abdominal mass accompanied by extensive heterogeneous aggregation. Both of them were highly suspected to be Wilms tumor, the most common renal malignant tumor in children. However, histopathological examination after surgery confirmed congenital mesodermal nephroma., Competing Interests: Conflicts of interest and sources of funding: none declared., (Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.)

Competing Interests: Conflict of Interest: The authors declare that there is no conflict of interest.

Clinical/methodological Issue: Diagnosis and therapy of renal tumors in children and adolescents are standardized by study protocols from major international societies. Imaging plays a central role, and in Europe patients between the ages of 6 months and 14 years with renal tumors are referred to neoadjuvant chemotherapy without histological confirmation according to the study protocol due to the frequency of Wilms tumor., Standard Radiologic Methods: Ultrasound is used worldwide as the primary investigative procedure for suspected renal tumors. In Europe, magnetic resonance imaging (MRI) has become established for more advanced diagnosis. In addition to differential diagnosis, staging is crucial for therapy. According to current protocol, this includes computed tomography (CT) of the thorax for the evaluation of pulmonary metastases., Methodological Innovations: Diffusion-weighted MRI provides promising results for the differentiation of nephroblastoma subtypes in addition to improved detectability of tumor foci. However, sufficient evidence is lacking., Performance: Differentiation of Wilms tumor from the highly malignant non-Wilm tumors, such as malignant rhabdoid tumor and clear cell sarcoma of the kidney, remains inconclusive based on imaging alone. Differential diagnosis is, therefore, based on morphologic and epidemiologic criteria., Assessment: The high degree of standardization in the diagnosis and treatment of renal tumors in children and adolescents has led to a significant improvement in prognosis. Overall survival of patients with Wilms tumor is currently over 90%., (© 2023. The Author(s), under exclusive licence to Springer Medizin Verlag GmbH, ein Teil von Springer Nature.)

Rationale: Wilms' tumor (WT) is the most common pediatric kidney malignancy and is rarely found in adults. Nonspecific clinical symptoms and imaging features often lead to delayed diagnosis or misdiagnosis of adult WT, resulting in poor clinical outcomes. Ultrasound (US), as an efficient and noninvasive examination method, has been widely used in clinical diagnosis and treatment. Therefore, various US evidence is meaningful to improve understanding of adult WT characteristics in ultrasound., Patient Concerns: A 45-year-old female patient with uremia (regular hemodialysis for 13 years) with painless gross hematuria was diagnosed with a right kidney tumor penetrating to the lung. Preoperatively, B-mode ultrasonography showed an ill-defined hyperechoic mass in the right kidney, which revealed an unclear border, uneven internal echoes, and calcification. Besides, the internal blood flow signal of the tumor was detected. Contrast-enhanced ultrasound (CEUS) showed an uneven hyper-enhancement in the tumor ("fast in and slow out"). Contrast-enhanced computed tomography of the kidney indicated a similar result as the CEUS. Moreover, the chest CT identified multiple pulmonary metastatic nodules., Diagnoses: An ultrasound-guided percutaneous core needle biopsy of the tumor proceeded to make a definite diagnosis of adult WT (epithelial type)., Interventions: The patient was treated with tislelizumab., Outcomes: No progress was found to date., Lessons: We report the first case in which CEUS was performed in an adult WT patient with uremia and multiple pulmonary metastases. The features obtained by the US can help in the diagnosis of adult WT and direct further diagnostic procedures., Competing Interests: The authors have no funding and conflicts of interest to disclose., (Copyright © 2023 the Author(s). Published by Wolters Kluwer Health, Inc.)

Background: Deep learning (DL) is more and more widely used in children's medical treatment. In this study, we have developed a computed tomography (CT)-based DL model for identifying undiagnosed non-Wilms tumors (nWTs) from pediatric renal tumors., Methods: This study collected and analyzed the preoperative clinical data and CT images of pediatric renal tumor patients diagnosed by our center from 2008 to 2020, and established a DL model to identify nWTs noninvasively., Results: A total of 364 children who had been confirmed by histopathology with renal tumors from our center were enrolled, including 269 Wilms tumors (WTs) and 95 nWTs. For DL model development, all cases were randomly allocated to training set (218 cases), validation set (73 cases), and test set (73 cases). In the test set, the DL model achieved area under the curve of 0.831 (95% CI: 0.712-0.951) in discriminating WTs from nWTs, with the accuracy, sensitivity, and specificity of 0.781, 0.563, and 0.842, respectively. The sensitivity of our model was higher than a radiologist with 15 years of experience., Conclusions: We presented a DL model for identifying undiagnosed nWTs from pediatric renal tumors, with the potential to improve the image-based diagnosis., Impact: Deep learning model was used for the first time to identify pediatric renal tumors in this study. Deep learning model can identify non-Wilms tumors from pediatric renal tumors. Deep learning model based on computed tomography images can improve tumor diagnosis rate., (© 2023. The Author(s), under exclusive licence to the International Pediatric Research Foundation, Inc.)

Malignant renal tumors account for approximately 6% of pediatric malignancies, with Wilms tumor (WT) representing approximately 90% of pediatric renal tumors. This paper provides consensus-based imaging guidelines for the initial evaluation of a child with suspected WT and follow-up during and after therapy co-developed by the Children's Oncology Group (COG) Diagnostic Imaging and Society for Pediatric Radiology (SPR) oncology committees. The guidelines for Wilms Tumor Imaging in the Society of International Pediatric Oncology (SIOP) are briefly discussed to highlight some of the differences in imaging approach., (© 2022 Wiley Periodicals LLC.)

Neuroblastoma, Wilms tumor, and hepatoblastoma are the most common pediatric abdominal malignancies. Management of these diseases is a multidisciplinary process that continues to evolve based on the results of international collaborative trials and advances in understanding of tumor biology. Each of these tumors has unique characteristics and behavior which are reflected in their respective staging systems. It is important for clinicians involved in the care of children with abdominal malignancies to be familiar with current staging guidelines and imaging recommendations. This article reviews the current role of imaging in the management of these common pediatric abdominal malignancies, with emphasis on initial staging., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier Inc.)

Background: Pediatric renal tumors are often heterogeneous lesions with variable regions of distinct histopathology. Direct comparison between in vivo imaging and ex vivo histopathology might be useful for identification of discriminating imaging features., Objective: This feasibility study explored the use of a patient-specific three-dimensional (3D)-printed cutting guide to ensure correct alignment (orientation and slice thickness) between magnetic resonance imaging (MRI) and histopathology., Materials and Methods: Before total nephrectomy, a patient-specific cutting guide based on each patient's preoperative renal MRI was generated and 3-D printed, to enable consistent transverse orientation of the histological specimen slices with MRI slices. This was expected to result in macroscopic slices of 5 mm each. The feasibility of the technique was determined qualitatively, through questionnaires administered to involved experts, and quantitatively, based on structured measurements including overlap calculation using the dice similarity coefficient., Results: The cutting guide was used in eight Wilms tumor patients receiving a total nephrectomy, after preoperative chemotherapy. The median age at diagnosis was 50 months (range: 4-100 months). The positioning and slicing of the specimens were rated overall as easy and the median macroscopic slice thickness of each specimen ranged from 5 to 6 mm. Tumor consistency strongly influenced the practical application of the cutting guide. Digital correlation of a total of 32 slices resulted in a median dice similarity coefficient of 0.912 (range: 0.530-0.960)., Conclusion: We report the feasibility of a patient-specific 3-D-printed MRI-based cutting guide for pediatric renal tumors, allowing improvement of the correlation of MRI and histopathology in future studies., (© 2022. The Author(s).)

Background: Compared to Wilms, non-Wilms renal tumors in children are less well understood due to their rare occurrence which limits precise definition of the typical imaging patterns., Objective: This study aims to identify distinctive imaging findings, demographic characteristics and prognosis of pediatric non-Wilms renal tumors., Materials and Methods: From January 2007 to December 2018, 207 patients with a diagnosis of primary kidney neoplasia were yielded from our radiology archive, 171 of whom were diagnosed with Wilms tumor, 4 with angiomyolipoma and one with nephrogenic rest. The remaining 31 patients with a diagnosis of primary kidney neoplasia were enrolled in this retrospective study. Imaging data, age, gender, prognosis and findings regarding follow-up were noted., Results: Eight patients had renal cell carcinoma, seven had clear cell sarcoma, six had mesoblastic nephroma, four had rhabdoid tumor, three had desmoplastic small round cell tumor, two had cystic nephroma and one had metanephric stromal tumor. The age of diagnosis was > 8 years for renal cell carcinoma and desmoplastic small round cell tumor, < 5 years for rhabdoid tumor and < 7 months for mesoblastic nephroma. There was no gender preference for any tumor type. The prognosis for rhabdoid tumor was extremely poor in that all the patients followed up in our institute were deceased, whereas no recurrence was found in other tumors. Translocation type renal cell carcinoma had lower T2-weighted signal intensity, mesoblastic nephroma was a predominantly cystic mass, clear cell sarcoma was generally larger at presentation and extensive amorphous calcifications were seen in desmoplastic small round cell tumor., Conclusion: For the differential diagnosis of pediatric non-Wilms renal tumors, age is the most important factor, followed by propensity to metastasize/aggressive behavior of the mass. Knowledge of specific imaging findings of these tumors may help to narrow the differential diagnosis., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Objectives: To investigate the extent to which observer variability of computed tomography (CT) lung nodule assessment may affect clinical treatment stratification in Wilms tumour (WT) patients, according to the recent Société Internationale d'Oncologie Pédiatrique Renal Tumour Study Group (SIOP-RTSG) UMBRELLA protocol., Methods: I: CT thoraces of children with WT submitted for central review were used to estimate size distribution of lung metastases. II: Scans were selected for blinded review by five radiologists to determine intra- and inter-observer variability. They assessed identical scans on two occasions 6 months apart. III: Monte Carlo simulation (MCMC) was used to predict the clinical impact of observer variation when applying the UMBRELLA protocol size criteria., Results: Lung nodules were found in 84 out of 360 (23%) children with WT. For 21 identified lung nodules, inter-observer limits of agreement (LOA) for the five readers were ±2.4 and ±1.4 mm (AP diameter), ±1.9 and ±1.8 mm (TS diameter) and ±2.0 and ±2.4 mm (LS diameter) at assessments 1 and 2. Intra-observer LOA across the three dimensions were ±1.5, ±2.2, ±3.5, ±3.1 and ±2.6 mm (readers 1-5). MCMC demonstrated that 17% of the patients with a 'true' nodule size of ≥3 mm will be scored as <3 mm, and 21% of the patients with a 'true' nodule size of <3 mm will be scored as being ≥3 mm., Conclusion: A significant intra-inter observer variation was found when measuring lung nodules on CT for patients with WT. This may have significant implications on treatment stratification, and thereby outcome, when applying a threshold of ≥3 mm for a lung nodule to dictate metastatic status., (© 2022 The Authors. Pediatric Blood & Cancer published by Wiley Periodicals LLC.)

Objectives: To examine the feasibility of performing ASL-MRI in paediatric patients with solid abdominal tumours., Methods: Multi-delay ASL data sets were acquired in ten paediatric patients diagnosed with either a neuroblastoma (n = 4) or nephroblastoma (n = 6) during a diagnostic MRI examination at a single visit (n = 4 at initial staging, n = 2 neuroblastoma and n = 2 nephroblastoma patients; n = 6 during follow-up, n = 2 neuroblastoma and n = 4 nephroblastoma patients). Visual evaluation and region-of-interest (ROI) analyses were performed on the processed perfusion-weighted images to assess ASL perfusion signal dynamics in the whole tumour, contralateral kidney, and tumour sub-regions with/without contrast enhancement., Results: The majority of the included abdominal tumours presented with relatively low perfusion-weighted signal (PWS), especially compared with the highly perfused kidneys. Within the tumours, regions with high PWS were observed which, at short PLD, are possibly related to labelled blood inside vessels and at long PLD, reflect labelled blood accumulating inside tumour tissue over time. Conversely, comparison of ASL perfusion-weighted image findings with T 1 w enhancement after contrast administration showed that regions lacking contrast enhancement also were void of PWS., Discussion: This pilot study demonstrates the feasibility of utilizing ASL-MRI in paediatric patients with solid abdominal tumours and provides a basis for further research on non-invasive perfusion measurements in this study population., (© 2021. The Author(s).)

Wilms tumor is the most common primary renal malignancy in pediatric age group, however, is rare in adults accounting for 0.5% of all adult renal malignancies. The histopathology is similar in both age groups, however the prognosis in adults is poor with tumor being at advanced stage at presentation with increased incidence of metastasis. Due to rare occurrence in adults and lack of differentiating clinical and imaging features its diagnosis is delayed or often misdiagnosed as adult renal cell cancer. Pre surgical or early post-surgical chemotherapy has shown significantly better surgical outcome and survival rate, however, delayed or misdiagnosis precludes or delays the chemotherapy. Lack of standardized treatment guidelines for adults also adds to the poor prognosis. Presurgical biopsy of renal masses in young adults can be suggested for early diagnosis as well as inclusion of presurgical chemotherapy for overall better outcome., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Horseshoe kidney (HK) refers to a congenital malformation that results from fusion of both the kidneys at one pole, and is the most common renal fusion defect with an incidence of 1 in 400 to 600 individuals. Synchronous bilateral development of Wilms tumor (WT) in an HK is extremely rare. Here, we present a case of synchronous bilateral WT in an HK in an 18-month-old girl. The patient received 12 weeks of preoperative chemotherapy followed by 2-step surgical resection including nephron-sparing surgery (NSS) in both kidneys and left nephrectomy because of positive surgical margin and adjuvant chemotherapy. The patient is still in remission and asymptomatic 6 months after the completion of treatment. In this report, we discuss the treatment modalities of synchronous bilaterally located WT in HK. We conclude that successful outcomes can be obtained with preoperative chemotherapy and NSS in such cases even in the presence of advanced disease and complex anatomic conditions. In addition, the deepest tumor point can be reached during NSS, but total nephrectomy should be considered regarding the possibility of microscopic residue., Competing Interests: The authors declare no conflict of interest., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

Background: We admitted a child with a duplex kidney combined with preoperative rupture of nephroblastoma and used this case to discuss the clinical features and treatment of this disease., Case Presentation: We retrospectively analyzed the clinical data of a 5-year-old girl with preoperative duplex kidney rupture combined with inferior nephroblastoma who was admitted to the Fourth Hospital of Baotou. In addition, we reviewed the relevant literature. The patient's details were as follows: weight, 17 kg; height, 108 cm; and body surface area, 0.7 m 2 . Abdominal ultrasound for abdominal pain revealed the presence of a left-sided renal mass; enhanced abdominal computed tomography further confirmed it to be a left-sided duplex kidney measuring approximately 6 × 5 × 5 cm, with a rupture originating from the lower kidney. The PubMed database was searched from 2010 to 2020 for the terms "Wilms' tumor" and "Duplex" and "Wilms' tumor" and "Rupture." The treatment plan was preoperative chemotherapy (vincristine/dactinomycin, VA regimen) + left kidney tumor radical surgery + postoperative chemotherapy (actinomycin-D/VCR/doxorubicin, AVD regimen). Postoperative pathology revealed an International Society of Pediatric Oncology intermediate-risk stage-3 nephroblastoma (mixed type) in the left kidney. Literature review was performed with 71 cases meeting the set criteria with an aim to analyze and summarize the clinical characteristics and treatment of patients with ruptured nephroblastoma and duplex kidney combined with nephroblastoma., Conclusions: To our knowledge, no previous studies have reported preoperative duplex kidney combined with nephroblastoma rupture. In patients with this condition, preoperative chemotherapy is recommended when the vital signs are stable and tumor resection can be performed after the tumor has shrunk to prevent secondary spread. If the patient's vital signs are unstable, emergency exploratory surgery is needed. If the nephroblastoma rupture is old and limited, surgery can be performed when the tumor size is small., (© 2021. The Author(s).)

The three most common pediatric solid tumors of the abdomen are neuroblastoma, Wilms tumor, and hepatoblastoma. These embryonal tumors most commonly present in the first decade of life. Each tumor has unique imaging findings, including locoregional presentation and patterns of distant spread. Neuroblastoma, Wilms tumor, and hepatoblastoma have unique staging systems that rely heavily on imaging and influence surgical and oncologic management. The staging systems include image-defined risk factors for neuroblastoma, the Children's Oncology Group staging system for Wilms tumor, and the pretreatment extent of tumor system (PRETEXT) for hepatoblastoma. It is important for radiologists to be aware of these staging systems to optimize image acquisition and interpretation. This article provides a practical and clinically oriented approach to the role of imaging in the staging of these common embryonal tumors of childhood. The selection among imaging modalities, key findings for determining tumor stage, and the role of imaging in posttreatment response evaluation and surveillance are discussed. Recent updates to the relevant staging systems are highlighted with attention to imaging findings of particular prognostic importance. The information presented will help radiologists tailor the imaging approach to the individual patient and guide optimal oncologic management.

Ganglioneuroma is an uncommon benign, slow-growing tumor arising from the neural crest. It rarely turns malignant even after decades of benign existence. Imaging modalities give a definite clue to the existence of a neurogenic mass but it is finally diagnosed on histopathology examination. Here, a 3-year-old girl presented with ganglioneuroma that mimicked renal mass on imaging in a tertiary care hospital, Dhaka, Bangladesh on January, 2016. Later on, it was confirmed as neuroganglioma by histopathological examination. As treatment differs widely between ganglioneuroma and nephroblastoma, a minor mistake in the accurate diagnosis may endanger the life of a patient through potential adverse effects of therapy. So, we should keep in mind about ganglioneuroma regarding evaluation of any kidney or abdominal masses.

Background: Nephroblastoma is the most common renal malignancy in children kidney. They are highly heterogeneous tumors with challenging imagistic and histopathological (HP) differential diagnosis. Imaging is critical for understanding local anatomy, staging and for planning surgical approach., Purpose: To determine whether HP staging can be successfully predicted by the imagistic staging using computed tomography. Also, we find it important to make a brief review of the imagistic, HP and immunohistochemical differential diagnosis of nephroblastoma, considering that a correct diagnosis is essential for an appropriate therapeutic strategy in all stages., Patients, Materials and Methods: We present a retrospective study of the medical dossiers of 22 patients that underwent surgery at our Center between 2014 and 2020. We provided descriptive data and compared imagistic and HP staging using a Mann-Whitney U-test. An up-to-date literature review was also done., Results: We found that imagistic staging tends to under- or over-stage at similar rates and that the difference between the two staging systems is statistically significant. Immunohistochemistry is necessary for establishing the correct diagnosis, especially in cases with one predominant HP pattern., Conclusions: HP and imagistic staging are not yet sufficiently similar for successfully predict the former via imagistic means.

Background: Horseshoe kidney (HK) is one of the most common renal fusion abnormalities, with an incidence of 1:400 in the normal population. However, Wilms tumor (WT) arising in an HK is a rare occurrence. We report the case of a 9-year-old boy who presented with an advanced WT in an HK and also highlight the management challenges in a resource-poor setting such as ours., Case Presentation: The patient was a 9-year-old Nigerian boy presented to the Pediatrics Outpatient Clinic of the University of Maiduguri Teaching Hospital (UMTH) with a history of progressive abdominal swelling, weight loss, abdominal pain, and cough. Abdominal examination revealed an irregular, firm, and non-tender mass in the right lumbar region. A computed tomography (CT) scan of the abdomen showed a heterogeneously dense mass that was predominantly to the right side of the abdomen and crossed the midline to the left side, where it continued with the relatively normal renal tissue. Chest CT revealed pulmonary metastases. A diagnosis of WT in an HK was made. The patient had a 6-week course of neoadjuvant chemotherapy, and a right nephrectomy and left partial nephrectomy was performed. The final histologic diagnosis of WT was made. Radiotherapy was intended but was not available in our facility, and the parents could not afford referral to another center., Conclusions: Children with a clinically suspected HK with WT should undergo a careful imaging evaluation such as CT before any surgical intervention. Neoadjuvant chemotherapy to reduce tumor bulk might be a good treatment method to reduce surgical morbidity and aid in complete excision and potential for preserving renal function., (© 2021. The Author(s).)

An identifiable genetic malformation or predisposition syndrome is present in 18% of Wilms tumor cases. Given this, children with conditions associated with a greater than 1% risk of developing Wilms tumor are recommended to have regular surveillance imaging with renal ultrasound until age 7. Seven years is the recommended screening duration because 95% of cases will occur by this age. We present a case of a child with isolated hemihypertrophy, associated with 5% risk of Wilms tumor, who presented with a tumor after the recommended screening, at age 9, brining into question the age cutoffs currently used., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Purpose: To assess the value of diffusion-weighted MRI (DW-MRI) in the non-invasive prediction of blastemal remnant after neoadjuvant chemotherapy in nephroblastoma., Methods: This IRB-approved study included 32 pediatric patients with 35 tumors who underwent DW-MRI prior and after completion of neoadjuvant chemotherapy and subsequent surgical resection. Two blinded radiologists volumetrically assessed each tumor on pre- and post-neoadjuvant images and the parameters mean ADC, median ADC, 12.5th/25th/75th ADC percentile, skewness, and kurtosis were calculated. Blastemal remnant was determined per the pathology report. Associations between imaging features and blastemal remnant quartiles were examined using the Kruskal-Wallis test and adjusted for false discovery rate., Results: Inter-reader agreement was high for mean ADC, skewness, kurtosis, and volume (ICC: 0.76-0.998). Pre-therapeutic histogram parameters skewness and kurtosis were found to be higher in patients with a higher amount of blastemal remnant for reader 1 (overall p = 0.035) and for kurtosis in reader 2 (overall p = 0.032) with skewness not reaching the level of statistical significance (overall p = 0.055). Higher tumor volume on pre-treatment imaging was associated with a higher amount of blastemal remnant after therapy (overall p = 0.032 for both readers)., Conclusions: Pre-treatment skewness and kurtosis of ADC histogram analysis were significantly associated with a larger fraction of a blastemal remnant after neoadjuvant chemotherapy. These findings could be incorporated into a more personalized chemotherapeutic regime in these patients and offer prognostic information at the time of initial diagnosis.

Clinical/methodological Issue: Renal tumors in children are treated according to the guidelines of the Renal Tumor Study Group of the International Society of Pediatric Oncology (SIOP-RTSG). Nephroblastoma is the most frequent renal tumor in children., Standard Radiological Methods: After sonography, magnetic resonance imaging (MRI) is the preferred imaging modality. The task of imaging includes differential diagnosis with the help of morphological and epidemiological criteria. Thorax computed tomography (CT) is introduced for initial staging., Methodological Innovations: Current studies of diffusion-weighted imaging (DWI)-MRI with analysis of the apparent diffusion coefficient (ADC) histogram indicate the potential to differentiate blastemal or anaplastic high-risk histology nephroblatoma subtypes. Imaging criteria for nephron-sparing surgery are defined and allow an individual therapy option in unilateral and especially in bilateral renal nephroblastoma., Performance: In addition to nephroblastoma, the differential diagnosis includes congenital mesoblastic nephroma, malignant rhabdoid tumor of the kidney, clear cell sarcoma and renal cell carcinoma. The diagnosis of nephrogenic rests and nephroblastomatosis is challenging., Achievements: Diagnostic standardization improves diagnosis and therapy of renal childhood tumors, and new prognostic markers may be introduced in the near future.

Objective: Clear cell sarcoma of the kidney (CCSK) is the second-most common but extremely rare primary renal malignancy in children after Wilms' tumor. The aims of this study were to evaluate the imaging features that could distinguish between CCSK and Wilms' tumor and to assess the features with diagnostic value for identifying CCSK., Materials and Methods: We reviewed the initial contrast-enhanced abdominal-pelvic CT scans of children with CCSK and Wilms' tumor between 2010 to 2019. Fifty-eight children (32 males and 26 females; age, 0.3-10 years), 7 with CCSK, and 51 with Wilms' tumor, were included. The maximum tumor diameter, presence of engorged perinephric vessels, maximum density of the tumor (Tmax) of the enhancing solid portion, paraspinal muscle, contralateral renal vein density, and density ratios (Tmax/muscle and Tmax/vein) were analyzed on the renal parenchymal phase of contrast-enhanced CT. Fisher's exact tests and Mann-Whitney U tests were conducted to analyze the categorical and continuous variables, respectively. Logistic regression and receiver operating characteristic curve analyses were also performed., Results: The age, sex, and tumor diameter did not differ between the two groups. Engorged perinephric vessels were more common in patients in the CCSK group (71% [5/7] vs. 16% [8/51], p = 0.005). Tmax (median, 148.0 vs. 111.0 Hounsfield unit, p = 0.004), Tmax/muscle (median, 2.64 vs. 1.67, p = 0.002), and Tmax/vein (median, 0.94 vs. 0.59, p = 0.002) were higher in the CCSK compared to the Wilms' group. Multiple logistic regression revealed that engorged vessels (odds ratio 13.615; 95% confidence interval [CI], 1.770-104.730) and Tmax/muscle (odds ratio 5.881; 95% CI, 1.337-25.871) were significant predictors of CCSK. The cutoff values of Tmax/muscle (86% sensitivity, 77% specificity) and Tmax/vein (71% sensitivity, 86% specificity) for the diagnosis of CCSK were 1.97 and 0.76, respectively., Conclusion: Perinephric vessel engorgement and greater tumor enhancement (Tmax/muscle > 1.97 or Tmax/vein > 0.76) are helpful for differentiating between CCSK and Wilms' tumor in children aged below 10 years., Competing Interests: The authors have no potential conflicts of interest to disclose., (Copyright © 2021 The Korean Society of Radiology.)

Objective: Denys-Drash syndrome (DDS) is defined by the triad of Wilms tumor, nephrotic syndrome, and/or ambiguous genitalia. Genetic testing may help identify new gene mutation sites and play an important role in clinical decision-making., Methods: We present a patient with an XY karyotype and female appearance, nephropathy, and Wilms tumor in the right kidney. Genomic DNA was extracted from peripheral blood cells according to standard protocols. "Next-generation" sequencing (NGS) was performed to identify novel variants. The variant was analyzed with Mutation Taster, and its function was explored by a cell growth inhibition assay., Results: We found the first case of Denys-Drash syndrome with the uncommon missense mutation (c.1420C>T, p.His474 Tyr) in the WT1 gene. In silico analysis, the variant was predicted "disease-causing" by Mutation Taster. The mutated variant showed a weaker effect in inhibiting tumor cells than wild-type WT1., Conclusions: The uncommon missense mutation (c.1420C>T, p.His474 Tyr) in the WT1 gene may be a crucial marker in DDS., (© 2021 The Authors. Journal of Clinical Laboratory Analysis published by Wiley Periodicals LLC.)

Renal tumors are rare in the neonatal period. Although some may be detected prenatally, a greater proportion present after birth, most often with a palpable abdominal mass with or without other associated symptoms. Cross-sectional imaging is typically followed by radical nephrectomy to make a specific histologic diagnosis to determine the need for additional therapy. This article reviews the clinical presentation, workup, treatment, and outcomes for neonates with some of the more common renal tumors seen in this population., Competing Interests: Disclosure The author has nothing to disclose., (Copyright © 2020 Elsevier Inc. All rights reserved.)

A 3-mo-old, female Boer goat was presented because of respiratory difficulties. Tachypnea and inspiratory dyspnea were noted during physical examination. Thoracic radiographs were unremarkable; however, upper airway and nasal passage radiographs revealed a soft tissue mass within the nasal passages. The patient underwent cardiorespiratory arrest and did not respond to resuscitation efforts during endoscopy. A large, pedunculated, semi-firm mass originated from the soft palate and obstructed 90% of the nasopharynx on autopsy. Histologically, the mass was composed of primitive cells that multifocally formed tubules and glomeruloid structures intermingled with areas of fusiform and blastemal cells. The neoplastic cells were positive for cytokeratin (tubular and glomeruloid cells), vimentin (fusiform population and blastemal cells), and Wilms tumor 1 protein (glomeruloid structures) on immunohistochemistry, consistent with a triphasic nephroblastoma. To our knowledge, nasopharyngeal nephroblastoma has not been reported previously in any species.

Introduction: Wilms' tumor (WT) is the most common type of malignant kidney tumor in children. Three-dimensional reconstructions can be performed pre-operatively to help surgeons in the planning phase., Objectives: The main objective of this study was to determine the variability of WT segmentation and 3D reconstruction. The secondary objectives were to assess the usefulness of these 3D reconstructions in the surgical planning phase and in the selection of patients for nephron-sparing surgery (NSS)., Methods: 14 scans from 12 patients were manually or semi-automatically segmented by 2 teams using 3D Slicer software. Inter-individual variability of 3D reconstructions was measured based on the Dice index. The utility of 3D reconstructions for the surgical planning was evaluated by 4 pediatric surgeons using a 5-point Likert scale. The possibility of undertaking NSS was evaluated according to the criteria defined in the Umbrella SIOP-RTSG 2016 protocol., Results: Segmentation of the WT, healthy kidney, pathological kidney, arterial and venous vascularization could be performed for all of the patients in this study. Urinary cavities segmentation could only be performed for 5 out of 14 scans that had a delayed acquisition phase. The mean time required to carry out these segmentations was 8.6 h [3-15 h]. The mean Dice index for all of the scans was good (mean: 0.87; range [0.83-0.91]). Considering each anatomical structure, the Dice index was very good for the WT (mean: 0.95; range [0.91-0.97]) and the healthy kidney (mean: 0.95; range [0.93-0.96]), good for the pathological kidney (mean: 0.87; range [0.69-0.96]) and arterial vascularization (mean: 0.84; range [0.74-0.91]). The Dice index was lower than 0.8 for venous vascularization only (mean: 0.77; range [0.58-0.86]). All the surgeons who were interviewed agreed that the 3D reconstructions were realistic representations and useful for the surgical planning phase. The images reconstructed in 3D allowed most of the criteria defined by the Umbrella SIOP-RTSG 2016 protocol to be evaluated regarding the selection of patients who could benefit from NSS., Conclusion: The inter-individual variability of 3D reconstructions of WT is acceptable. Three-dimensional representation appears to assist surgeons with the surgical planning phase by allowing them to better anticipate the operative risks. 3D reconstructions can also be an additional tool to better select patients for NSS. However, the manual or semi-automatic method used is very time-consuming, making it difficult for a routinely use. Developing techniques to automate this segmentation process, therefore, appears to be essential if surgeons and radiologists are to use it in daily practice., Competing Interests: Conflicts of interest No author has any potential conflict of interest., (Copyright © 2020 Journal of Pediatric Urology Company. Published by Elsevier Ltd. All rights reserved.)

Purpose: We previously developed an age-scalable 3D computational phantom that has been widely used for retrospective whole-body dose reconstructions of conventional two-dimensional historic radiation therapy (RT) treatments in late effects studies of childhood cancer survivors. This phantom is modeled in the FORTRAN programming language and is not readily applicable for dose reconstructions for survivors treated with contemporary RT whose treatment plans were designed using computed tomography images and complex treatment fields. The goal of this work was to adapt the current FORTRAN model of our age-scalable computational phantom into Digital Imaging and Communications in Medicine (DICOM) standard so that it can be used with any treatment planning system (TPS) to reconstruct contemporary RT. Additionally, we report a detailed description of the phantom's age-based scaling functions, information that was not previously published., Method: We developed a Python script that adapts our phantom model from FORTRAN to DICOM. To validate the conversion, we compared geometric parameters for the phantom modeled in FORTRAN and DICOM scaled to ages 1 month, 6 months, 1, 2, 3, 5, 8, 10, 15, and 18 years. Specifically, we calculated the percent differences between the corner points and volume of each body region and the normalized mean square distance (NMSD) between each of the organs. In addition, we also calculated the percent difference between the heights of our DICOM age-scaled phantom and the heights (50th percentile) reported by the World Health Organization (WHO) and Centers for Disease Control and Prevention (CDC) for male and female children of the same ages. Additionally, we calculated the difference between the organ masses for our DICOM phantom and the organ masses for two reference phantoms (from International Comission on Radiation Protection (ICRP) 89 and the University of Florida/National Cancer Institute reference hybrid voxel phantoms) for ages newborn, 1, 5, 10, 15 and adult. Lastly, we conducted a feasibility study using our DICOM phantom for organ dose calculations in a commercial TPS. Specifically, we simulated a 6 MV photon right-sided flank field RT plan for our DICOM phantom scaled to age 3.9 years; treatment field parameters and age were typical of a Wilms tumor RT treatment in the Childhood Cancer Survivor Study. For comparison, the same treatment was simulated using our in-house dose calculation system with our FORTRAN phantom. The percent differences (between FORTRAN and DICOM) in mean dose and percent of volume receiving dose ⩾5 Gy were calculated for two organs at risk, liver and pancreas., Results: The percent differences in corner points and the volumes of head, neck, and trunk body regions between our phantom modeled in FORTRAN and DICOM agreed within 3%. For all of the ages, the NMSDs were negliglible with a maximum NMSD of 7.80 × 10 -2 mm for occiptital lobe of 1 month. The heights of our age-scaled phantom agreed with WHO/CDC data within 7% from infant to adult, and within 2% agreement for ages 5 years and older. We observed that organ masses in our phantom are less than the organ masses for other reference phantoms. Dose calculations done with our in-house calculation system (with FORTRAN phantom) and commercial TPS (with DICOM phantom) agreed within 7%., Conclusion: We successfully adapted our phantom model from the FORTRAN language to DICOM standard and validated its geometric consistency. We also demonstrated that our phantom model is representative of population height data for infant to adult, but that the organ masses are smaller than in other reference phantoms and need further refinement. Our age-scalable computational phantom modeled in DICOM standard can be scaled to any age at RT and used within a commercial TPS to retrospectively reconstruct doses from contemporary RT in childhood cancer survivors.

Purpose: To assess the value of diffusion-weighted MRI in the pre-therapeutic evaluation of pediatric renal cortical tumors., Methods: This IRB-approved, retrospective multi-center study included 122 pediatric patients with 130 renal tumors, who underwent MRI including DWI before neoadjuvant chemotherapy and nephrectomy. Two radiologists independently assessed each tumor volumetrically, and apparent diffusion coefficient (ADC) values were calculated on a voxel-wise basis, including parameters derived from histogram and texture analysis., Results: Inter-reader agreement was excellent (ICC 0.717-0.975). For both readers, patients with locally aggressive tumor growth (SIOP 3 stage) or with metastases (M1) had significantly lower 12.5th-percentile ADC values (p ≤ 0.028) compared to those with lower-stage tumors, and the parameter energy differed significantly between patients with M1 and those with M0 status (p ≤ 0.028). Contrast and homogeneity differed significantly between benign nephroblastomatosis and malignant nephroblastoma (p ≤ 0.045, both readers). As compared to all other subtypes, the blastemal subtype demonstrated significantly higher skewness (p ≤ 0.022, both readers) and the diffuse anaplastic subtype demonstrated significantly higher 75th-percentile ADC values (p ≤ 0.042, both readers)., Conclusions: Diffusion-weighted MRI may be of value in identifying benign nephroblastomatosis and assessing nephroblastoma subtypes. Therefore, further research is warranted to assess its value in risk stratification for pediatric patients with renal tumors in the future.

The radiological distinction of Wilms tumor (WT) nodules from nephrogenic rests (NR) in patients with multifocal unilateral WT or bilateral disease is challenging. The study aims to compare the radiology assessment of kidney nodules with their final histology in 48 patients. The final histology of 118 nodules corresponded to the initial radiological diagnosis while 40 (25%) nodules were misdiagnosed, 20 being initially diagnosed WT on imaging were proved to be NR at histology. The size of nodules at diagnosis might help to distinguish WT from NR before surgery. Homogeneity did not seem to be a key feature., (© 2020 Wiley Periodicals, Inc.)

Ureteral extension of childhood renal tumors is exceedingly rare. Hematuria, hydronephrosis, poorly or nonfunctioning kidney should raise suspicion for ureteral tumor extension. Identifying ureteral extension on preoperative imaging or intraoperatively before ureteral transection is crucial to obtain good oncological outcome without unnecessary exposure to radiation therapy or more intensive chemotherapy. In this report, we present three children with cystic renal tumors extending into the ureter and review the relevant literature., (Copyright © 2020 Elsevier Inc. All rights reserved.)

A 1-year-old male mixed breed dog presented for the evaluation of progressive hindlimb paresis. Neurological examination indicated a spinal cord lesion between the 3rd thoracic and 3rd lumbar vertebrae. Magnetic resonance imaging (MRI) revealed an intramedullary spinal cord lesion located at the level of the 1st and 2nd lumbar vertebrae. Following cytoreductive surgery of the mass, palliative radiation therapy was administered. A diagnosis of nephroblastoma was made based on histological examination. After radiation therapy, the disappearance of the spinal lesion was confirmed by MRI. The dog was improved from gait abnormality and alive at 16 months postoperatively, with slight signs of neurological dysfunction.

OBJECTIVE. Distinguishing nephrogenic rests from small Wilms tumors can be challenging. This retrospective study was performed to determine if imaging characteristics can be used to distinguish nephrogenic rests from Wilms tumors. MATERIALS AND METHODS. All cases of pathologically confirmed nephrogenic rests and Wilms tumors smaller than 5 cm in maximum dimension on imaging in patients younger than 5 years old were identified from the Children's Oncology Group AREN03B2 study (July 2006-August 2016). Exclusion criteria were chemotherapy before pathologic evaluation or more than 30 days between imaging and surgery; in addition, patients with nephrogenic rests occurring within or juxtaposed to a Wilms tumor and patients with diffuse hyperplastic perilobar nephroblastomatosis were excluded. Two radiologists who were blinded to pathology results assessed all lesions. The two-sample t test was used for continuous variables, and the Fisher exact test was used for categoric variables. ROC analysis was performed to determine the optimal size cutoff for distinguishing between nephrogenic rests and Wilms tumors. RESULTS. Thirty-one pathologically confirmed rests (20 perilobar, 11 intralobar) and 26 Wilms tumors smaller than 5 cm met the eligibility criteria for study inclusion. The median diameter of the nephrogenic rests was 1.3 cm (range, 0.7-3.4 cm) and the median diameter of the Wilms tumor was 3.2 cm (range, 1.8-4.9 cm) ( p < 0.001). Imaging findings supportive of Wilms tumors were spherical ( p < 0.001) and exophytic ( p < 0.001) lesions. Perilobar rests (17/20) were more likely to be homogeneous than intralobar rests (3/11) or Wilms tumor (3/26) ( p < 0.001). ROC analysis showed that the optimal size cutoff for distinguishing between nephrogenic rests and Wilms tumors was 1.75 cm. CONCLUSION. In children younger than 5 years old, the diagnosis of a Wilms tumor should be favored over a nephrogenic rest when a renal mass is spherical, exophytic, or larger than 1.75 cm. Homogeneity favors the diagnosis of perilobar nephrogenic rests, whereas intralobar rests and Wilms tumors are more likely to be inhomogeneous.

Wilms tumor (WT) is the most common renal malignancy of childhood and accounts for 6% of all childhood malignancies. With current therapies, the 5-yr overall survival (OS) for children with unilateral favorable histology WT is greater than 85%. The prognosis is worse, however, for the roughly 15% of patients who relapse, with only 50%-80% OS reported in those with recurrence. Herein, we describe the extended and detailed clinical course of a rare case of a child with recurrent, pulmonary metastatic, favorable histology WT harboring a BRAF V600E mutation. The BRAF V600E mutation, commonly found in melanoma and other cancers, and previously undescribed in WT, has recently been reported by our group in a subset of epithelial-predominant WT. This patient, who was included in that series, presented with unilateral, stage 1, favorable histology WT and was treated with standard chemotherapy. Following the completion of therapy, the patient relapsed with pulmonary metastatic disease, that then again recurred despite an initial response to salvage chemotherapy and radiation. Next-generation sequencing (NGS) on the metastatic pulmonary nodule revealed a BRAF V600E mutation. After weighing the therapeutic options, a novel approach with dual BRAF/MEK inhibitor combination therapy was initiated. Complete radiographic response was observed following 4 months of therapy with dabrafenib and trametinib. At 12 months following the start of BRAF/MEK combination treatment, the patient continues with a complete response and has experienced minimal treatment-related side effects. This represents the first case, to our knowledge, of effective treatment with BRAF/MEK molecularly targeted therapy in a pediatric Wilms tumor patient., (© 2020 Obasaju et al.; Published by Cold Spring Harbor Laboratory Press.)