Wilms tumour is the most common renal malignancy of childhood. It is curable in the majority of children, albeit at considerable cost in terms of treatment related late effects in some children. In the small group of 'high risk' Wilms tumours, the prognosis is much worse. Overall, one in ten children with Wilms tumour will still die of their disease despite modern treatment approaches.The genetic changes underpinning Wilms tumour have been defined by studies of familial cases and more recently, by unbiased DNA sequencing of tumour genomes. Together these have defined the landscape of cancer genes that are operative in Wilms tumour. Many are intricately linked to control of fetal nephrogenesis. Here, we review our current understanding of germline and somatic genetic changes that underlie Wilms tumour. A -Introduction A1. Brief overview 1.1 What is it?Wilms tumour (WT), also known as nephroblastoma, is one of the so-called embryonal tumours of childhood, due to its histological mimicry of stages in nephrogenesis and its early age of onset. It accounts for 90% of childhood renal tumours and constitutes 7% of all childhood cancers(1). Thought to arise from aberrant nephrogenesis, many of the genetic changes underpinning WT occur in genes involved in fetal nephrogenesis(2). Although our understanding of tumourigenesis remains incomplete, the WNT pathway and insulin-like growth factor (IGF) signaling have long been considered to have pathogenic roles. This review follows recent large scale analyses interrogating the somatic basis of WT. The genetic changes underpinning WT are diverse, driven by an array of almost 40 cancer genes (Table 1). Such diversity is particularly surprising given the monotonous driver landscape of other childhood renal tumours, such as clear cell sarcoma of the kidney (CCSK) or congenital mesoblastic nephroma (CMN). In comparison to adult cancers, the median somatic mutation rate is far lower in WT, 0.17 per million bases

Retinoblastoma (Rb) is the most common primary intraocular malignancy of childhood, but an uncommon paediatric cancer, with a constant incidence worldwide of 1:15,000-1:20,000 live births. Despite its rarity, Rb has served as a cornerstone in the field of oncology in many of the aspects that comprise cancer management, including classification schemes, treatment modalities, genetic testing and screening. Until just over half a century ago, the major treatment for Rb was eye removal, and prognosis was poor with outcome fatal for most children. The dramatic evolution, in a short period of time across all fields of Rb management, as well as the development of specialized centres, better infrastructure and introduction of awareness campaigns, has resulted in nearly 100% survival in developed countries and allowed eye salvage in many of the cases. External beam radiotherapy was used as the main treatment choice for four decades, but replaced by chemotherapy at the turn of the century. Initially, and still in many centres, chemotherapy is administered intravenously, but recently is targeted directly into the eye by means of intra-ophthalmic artery and intravitreal chemotherapy. To date, a range of treatments is available to the Rb expert, including enucleation, but there is lack of consensus in a number of scenarios as to what to use and when. In such a rare cancer, treatment outcomes are reported usually via retrospective analyses, with few prospective randomized controlled trials. Classification schemes have also evolved following the introduction of new treatment modalities, but discrepancies exist among centres with respect to the preferred schema and its interpretation. Retinoblastoma management is a remarkable success story, but the future will require a collaborative effort in the form of multicentre randomized controlled trials in order to further improve the quality of care for this subset of young children with ocular cancer.

Adult cancers often arise from premalignant clonal expansions. Whether the same is true of childhood tumors has been unclear. To investigate whether Wilms tumor (nephroblastoma; a childhood kidney cancer) develops from a premalignant background, we examined the phylogenetic relationship between tumors and corresponding normal tissues. In 14 of 23 cases studied (61%), we found premalignant clonal expansions in morphologically normal kidney tissues that preceded tumor development. These clonal expansions were defined by somatic mutations shared between tumor and normal tissues but absent from blood cells. We also found hypermethylation of the H19 locus, a known driver of Wilms tumor development, in 58% of the expansions. Phylogenetic analyses of bilateral tumors indicated that clonal expansions can evolve before the divergence of left and right kidney primordia. These findings reveal embryonal precursors from which unilateral and multifocal cancers develop.

Background WAGR syndrome (Wilms tumor, aniridia, genitourinary anomalies, and range of developmental delays) is a rare contiguous gene deletion syndrome with a 45% to 60% risk of developing Wilms tumor (WT). Currently, surveillance and treatment recommendations are based on limited evidence. Methods Clinical characteristics, treatments, and outcomes were analyzed for patients with WAGR and WT/nephroblastomatosis who were identified through International Society of Pediatric Oncology Renal Tumor Study Group (SIOP‐RTSG) registries and the SIOP‐RTSG network (1989‐2019). Events were defined as relapse, metachronous tumors, or death. Results Forty‐three patients were identified. The median age at WT/nephroblastomatosis diagnosis was 22 months (range, 6‐44 months). The overall stage was available for 40 patients, including 15 (37.5%) with bilateral disease and none with metastatic disease. Histology was available for 42 patients; 6 nephroblastomatosis without further WT and 36 WT, including 19 stromal WT (52.8%), 12 mixed WT (33.3%), 1 regressive WT (2.8%) and 2 other/indeterminable WT (5.6%). Blastemal type WT occurred in 2 patients (5.6%) after prolonged treatment for nephroblastomatosis; anaplasia was not reported. Nephrogenic rests were present in 78.9%. Among patients with WT, the 5‐year event‐free survival rate was 84.3% (95% confidence interval, 72.4%‐98.1%), and the overall survival rate was 91.2% (95% confidence interval, 82.1%‐100%). Events (n = 6) did not include relapse, but contralateral tumor development (n = 3) occurred up to 7 years after the initial diagnosis, and 3 deaths were related to hepatotoxicity (n = 2) and obstructive ileus (n = 1). Conclusions Patients with WAGR have a high rate of bilateral disease and no metastatic or anaplastic tumors. Although they can be treated according to existing WT protocols, intensive monitoring of toxicity and surveillance of the remaining kidney(s) are advised. Lay Summary WAGR syndrome (Wilms tumor, aniridia, genitourinary anomalies, and range of developmental delays) is a rare genetic condition with an increased risk of developing Wilms tumor. In this study, 43 patients with WAGR and Wilms tumor (or Wilms tumor precursor lesions/nephroblastomatosis) were identified through the international registry of the International Society of Pediatric Oncology Renal Tumor Study Group (SIOP‐RTSG) and the SIOP‐RTSG network. In many patients (37.5%), both kidneys were affected. Disease spread to other organs (metastases) did not occur. Overall, this study demonstrates that patients with WAGR syndrome and Wilms tumor can be treated according to existing protocols. However, intensive monitoring of treatment complications and surveillance of the remaining kidney(s) are advised.