Apparent diffusion coefficient as it relates to histopathology findings in post-chemotherapy nephroblastoma: a feasibility study

MRI Characteristics of Pediatric and Young-Adult Renal Cell Carcinoma: A Single-Center Retrospective Study and Literature Review

Pediatric renal cell carcinoma (RCC) is a rare malignancy. Magnetic resonance imaging (MRI) is the preferred imaging modality for assessment of these tumors. The previous literature has suggested that cross-sectional-imaging findings differ between RCC and other pediatric renal tumors and between RCC subtypes. However, studies focusing on MRI characteristics are limited. Therefore, this study aims to identify MRI characteristics of pediatric and young-adult RCC, through a single-center case series and literature review. Six identified diagnostic MRI scans were retrospectively assessed, and an extensive literature review was conducted. The included patients had a median age of 12 years (63-193 months). Among other subtypes, 2/6 (33%) were translocation-type RCC (MiT-RCC) and 2/6 (33%) were clear-cell RCC. Median tumor volume was 393 cm³ (29-2191 cm³). Five tumors had a hypo-intense appearance on T2-weighted imaging, whereas 4/6 were iso-intense on T1-weighted imaging. Four/six tumors showed well-defined margins. The median apparent diffusion coefficient (ADC) values ranged from 0.70 to 1.20 × 10^-3 mm²/s. In thirteen identified articles focusing on MRI characteristics of MiT-RCC, the majority of the patients also showed T2-weighted hypo-intensity. T1-weighted hyper-intensity, irregular growth pattern and limited diffusion-restriction were also often described. Discrimination of RCC subtypes and differentiation from other pediatric renal tumors based on MRI remains difficult. Nevertheless, T2-weighted hypo-intensity of the tumor seems a potential distinctive characteristic.

Nephron-sparing surgery for Wilms tumor

The algorithm that has been used successfully in the surgical management of unilateral Wilms tumor, radical nephroureterectomy, cannot be used in children who present with synchronous bilateral renal masses. Instead, a surgical approach that removes all tumor masses while preserving as much normal renal parenchyma as possible is encouraged to avoid acute and long-term renal insufficiency. We will review technical aspects of the conduct of nephron-sparing surgery for synchronous bilateral Wilms tumor, including the more recent advances in the use of imaging adjuncts such as pre-operative 3D imaging and fluorescence-guided surgery. The potential role of nephron-sparing surgery for unilateral Wilms tumor will also be discussed.

Direct correlation of MRI with histopathology in pediatric renal tumors through the use of a patient-specific 3-D-printed cutting guide: a feasibility study

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.

Quantitative abdominal magnetic resonance imaging in children-special considerations

The use of quantitative MRI methods for assessment of the abdomen in children has become commonplace over the past decade. Increasingly employed methods include MR elastography, chemical shift encoded (CSE) MR imaging for determination of proton density fat fraction, diffusion-weighted imaging, and a variety of relaxometry techniques, such as T1 and T2* mapping. These techniques can be used in a variety of settings to distinguish normal from abnormal tissue as well as determine the severity of disease. The performance of quantitative MRI methods in the pediatric population presents unique challenges as compared to adult populations. These challenges relate to multiple factors, including patient size, pediatric physiology, inability to breath hold, and greater physical motion during the examination. The purpose of this review article is to review quantitative MRI methods that may be used in clinical practice to assess the pediatric abdomen and to discuss special considerations when performing these techniques in children.

Multidisciplinary Treatment Strategies for Wilms Tumor: Recent Advances, Technical Innovations and Future Directions

Significant progress has been made in the management of Wilms tumor (WT) in recent years, mostly as a result of collaborative efforts and the implementation of protocol-driven, multimodal therapy. This article offers a comprehensive overview of current multidisciplinary treatment strategies for WT, whilst also addressing recent technical innovations including nephron-sparing surgery (NSS) and minimally invasive approaches. In addition, surgical concepts for the treatment of metastatic disease, advances in tumor imaging technology and potentially prognostic biomarkers will be discussed. Current evidence suggests that, in experienced hands and selected cases, laparoscopic radical nephrectomy and laparoscopic-assisted partial nephrectomy for WT may offer the same outcome as the traditional open approach. While NSS is the standard procedure for bilateral WT, NSS has evolved as an alternative technique in patients with smaller unilateral WT and in cases with imminent renal failure. Metastatic disease of the lung or liver that is associated with WT is preferably treated with a three-drug chemotherapy and local radiation therapy. However, surgical sampling of lung nodules may be advisable in persistent nodules before whole lung irradiation is commenced. Several tumor markers such as loss of heterozygosity of chromosomes 1p/16q, 11p15 and gain of function at 1q are associated with an increased risk of recurrence or a decreased risk of overall survival in patients with WT. In summary, complete resection with tumor-free margins remains the primary surgical aim in WT, while NSS and minimally invasive approaches are only suitable in a subset of patients with smaller WT and low-risk disease. In the future, advances in tumor imaging technology may assist the surgeon in defining surgical resection margins and additional biomarkers may emerge as targets for development of new diagnostic tests and potential therapies.

Wilms tumour

Wilms tumour (WT) is a childhood embryonal tumour that is paradigmatic of the intersection between disrupted organogenesis and tumorigenesis. Many WT genes play a critical (non-redundant) role in early nephrogenesis. Improving patient outcomes requires advances in understanding and targeting of the multiple genes and cellular control pathways now identified as active in WT development. Decades of clinical and basic research have helped to gradually optimize clinical care. Curative therapy is achievable in 90% of affected children, even those with disseminated disease, yet survival disparities within and between countries exist and deserve commitment to change. Updated epidemiological studies have also provided novel insights into global incidence variations. Introduction of biology-driven approaches to risk stratification and new drug development has been slower in WT than in other childhood tumours. Current prognostic classification for children with WT is grounded in clinical and pathological findings and in dedicated protocols on molecular alterations. Treatment includes conventional cytotoxic chemotherapy and surgery, and radiation therapy in some cases. Advanced imaging to capture tumour composition, optimizing irradiation techniques to reduce target volumes, and evaluation of newer surgical procedures are key areas for future research.

Diffusion-weighted MRI and histogram analysis: assessment of response to neoadjuvant chemotherapy in nephroblastoma

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.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00261-021-03032-9.

[Imaging of renal tumors in children]

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.

Characteristics and outcome of pediatric renal cell carcinoma patients registered in the International Society of Pediatric Oncology (SIOP) 93-01, 2001 and UK-IMPORT database: A report of the SIOP-Renal Tumor Study Group

In children, renal cell carcinoma (RCC) is rare. This study is the first report of pediatric patients with RCC registered by the International Society of Pediatric Oncology-Renal Tumor Study Group (SIOP-RTSG). Pediatric patients with histologically confirmed RCC, registered in SIOP 93-01, 2001 and UK-IMPORT databases, were included. Event-free survival (EFS) and overall survival (OS) were analyzed using the Kaplan-Meier method. Between 1993 and 2019, 122 pediatric patients with RCC were registered. Available detailed data (n = 111) revealed 56 localized, 30 regionally advanced, 25 metastatic and no bilateral cases. Histological classification according to World Health Organization 2004, including immunohistochemical and molecular testing for transcription factor E3 (TFE3) and/or EB (TFEB) translocation, was available for 65/122 patients. In this group, the most common histological subtypes were translocation type RCC (MiT-RCC) (36/64, 56.3%), papillary type (19/64, 29.7%) and clear cell type (4/64, 6.3%). One histological subtype was not reported. In the remaining 57 patients, translocation testing could not be performed, or TFE-cytogenetics and/or immunohistochemistry results were missing. In this group, the most common RCC histological subtypes were papillary type (21/47, 44.7%) and clear cell type (11/47, 23.4%). Ten histological subtypes were not reported. Estimated 5-year (5y) EFS and 5y OS of the total group was 70.5% (95% CI = 61.7%-80.6%) and 84.5% (95% CI = 77.5%-92.2%), respectively. Estimated 5y OS for localized, regionally advanced, and metastatic disease was 96.8%, 92.3%, and 45.6%, respectively. In conclusion, the registered pediatric patients with RCC showed a reasonable outcome. Survival was substantially lower for patients with metastatic disease. This descriptive study stresses the importance of full, prospective registration including TFE-testing.

New approaches to risk stratification for Wilms tumor

PURPOSE OF REVIEW

The treatment of Wilms tumor is one of the great achievements in the field of oncology. One of the key success factors has been improved risk stratification, enabling augmentation or reduction of therapy depending on a patient's risk of relapse. This article highlights the evolution of clinical and biological prognostic markers that have been applied in the treatment of Wilms tumor.

RECENT FINDINGS

Historically, tumor stage and histology were the sole determinants of Wilms tumor treatment. Recent clinical trials conducted by the Children's Oncology Group (COG) and the International Society of Pediatric Oncology (SIOP) Renal Tumor Study Group have expanded the menu of prognostic factors to include histologic and volumetric response to therapy and tumor-specific loss of heterozygosity (LOH) at chromosomes 1p and 16q. Augmentation of therapy has been able to overcome the adverse risk factors. An emerging prognostic marker is chromosome 1q gain, will be incorporated into future clinical trials.

SUMMARY

The application of new clinical and biological prognostic factors has created unprecedented ability to tailor therapy for Wilms tumor, accompanied with improved outcomes. Current and future trials will continue to enhance precision medicine for Wilms tumor.

Imaging of childhood urologic cancers: current approaches and new advances

Urologic tumors make up approximately 10% of all pediatric cancers, and include a variety of different histologies and imaging considerations. In this review, we discuss standard radiologic approaches for children with tumors arising in the genitourinary system, and identify important ways in which imaging affects the differential diagnosis, preoperative planning, and staging of these tumors. In addition, we provide an update on strategies to reduce the time of imaging, which may obviate the need for sedation in younger patients. Efforts to reduce a patient’s overall radiation exposure and subsequent risk of second malignancy are also detailed, including recent work on surveillance imaging following completion of therapy. Finally, we highlight new techniques such as radiomics that are now being investigated for patients with these malignancies.

Radiological response and histological findings in nephroblastoma: Is the any correlation?

INTRODUCTION

The Sociétè Internationale d'Oncologie Pédiatrique advocates for neoadjuvant chemotherapy in the management of nephroblastoma. Postoperatively, histological findings are used to assign risk classification to resected tumours. The aim of this study is to compare the response demonstrated by pre-operative imaging to the amount of necrosis seen on histology postoperatively.

PATIENTS AND METHODS

About 33 patients with nephroblastoma over a 10 year period had adequate imaging and histology records for this study. Three methods were used to assess tumour change following neoadjuvant therapy and were compared with histological records. 1. An estimation of necrosis, 2. Surface areas of apparent necrosis within the tumour measured on static imaging, 3. The change in volume of the mass. Pearson coefficient was calculated to measure the correlation between histologically observed necrosis and radiological changes. Results were considered significant if P< 0.05.

RESULTS

There was no correlation between radiological changes on pre-operative imaging and the percentage of necrosis seen on histology. Change in tumour size on radiological studies showed a moderate correlation to percentage tumour necrosis on histology but was unable to predict tumour risk classification.

CONCLUSIONS

In nephroblastoma, there is a moderate correlation between the decrease in size of a mass noted on imaging following chemotherapy and the degree of necrosis found postoperatively on histology. Change in tumour size cannot be used to predict histological risk classification. It is not possible to predict the histological risk classification of a nephroblastoma based on the changes demonstrated on non-contrasted magnetic resonance imaging or computed tomography preoperatively.

Renal Tumors of Childhood-A Histopathologic Pattern-Based Diagnostic Approach

Renal tumors comprise approximately 7% of all malignant pediatric tumors. This is a highly heterogeneous group of tumors, each with its own therapeutic management, outcome, and association with germline predispositions. Histopathology is the key in establishing the correct diagnosis, and therefore pathologists with expertise in pediatric oncology are needed for dealing with these rare tumors. While each tumor shows different histologic features, they do have considerable overlap in cell type and histologic pattern, making the diagnosis difficult to establish, if based on routine histology alone. To this end, ancillary techniques, such as immunohistochemistry and molecular analysis, can be of great importance for the correct diagnosis, resulting in appropriate treatment. To use ancillary techniques cost-effectively, we propose a pattern-based approach and provide recommendations to aid in deciding which panel of antibodies, supplemented by molecular characterization of a subset of genes, are required.

European Society of Paediatric Radiology abdominal imaging task force: recommendations for contrast-enhanced ultrasound and diffusion-weighted imaging in focal renal lesions in children

Contrast-enhanced ultrasound (CEUS) and diffusion-weighted imaging (DWI) are safe, repeatable imaging techniques. The aim of this paper is to discuss the advantages, technical factors and possible clinical applications of these imaging tools in focal renal lesions in children.

[Imaging of abdominal tumors in childhood and adolescence : Part II: relevant intra-abdominal and retroperitoneal tumor entities]

Abdominal and pelvic tumors in children and adolescents can be manifested intra-abdominally and also often in the retroperitoneum. The most important pediatric primary retroperitoneal space-occupying lesions are nephroblastoma (Wilms' tumor) and neuroblastoma, whereby imaging plays a decisive role in the diagnostics and differentiation of the two entities. Benign tumors of the mesentery and gastrointestinal tract occur more frequently in children than malignant lesions. The benign entities include lipoma, polyps and vascular tumors, such as lymphatic malformations. Of the malignant sarcomas, abdominal rhabdomyosarcomas (RMS) occur relatively often in childhood and adolescence. The most frequent pediatric abdominal lymphoma is Burkitt's lymphoma, an aggressive subtype of non-Hodgkin's lymphoma. Relevant tumor entities in childhood are also germ cell tumors, which originate from the genitals (gonadal) or can be extragonadally manifested. The benignancy or malignancy of germ cell tumors ranges from benign teratomas to highly malignant entities, such as yolk sac tumors. The germ cell tumors, just as all pediatric abdominal mass lesions, show a broad spectrum of tumor aggressiveness, malignancy and therefore also prognosis and mortality for the affected children and adolescents.

European Society of Paediatric Radiology 2019 strategic research agenda: improving imaging for tomorrow's children

The European Society of Paediatric Radiology (ESPR) research committee was established to initiate, drive forward and foster excellence in paediatric imaging, paediatric image-guided intervention and radiation protection research, by facilitating more evidence-based standards, protocols and multi-institutional collaborations. The ESPR Strategic Research Agenda outlines our current research approach, highlighting several areas of paediatric imaging where the society can help guide current and future research, and emphasizing those areas where early research ("seed") funding may need to be allocated by this and other societies as precursors to larger grant applications. The key aims are to evaluate normal variation in order to be able to confidently diagnose disease states, develop robust image-based classification systems to aid diagnosis and treatment monitoring, and help develop evidence-based clinical guidelines using current literature and experience to identify knowledge gaps. For this reason, the development of evidence-based imaging pipelines, broken down step-by-step to include diagnosis, classification and clinical effectiveness, should be the end goal for each disease entity for each affected child. Here, we outline the 2019 ESPR Strategic Research Agenda along three points in the clinical imaging pipeline: clinical referral, disease diagnosis and evolution, and clinical therapeutic evaluation and effectiveness. Through multicentre trials, using existing high-level experience and expertise, and nurturing the next generation of researchers, we will be able to achieve these aims.

Comparison of 3-Dimensional and Augmented Reality Kidney Models With Conventional Imaging Data in the Preoperative Assessment of Children With Wilms Tumors

IMPORTANCE

Nephron-sparing surgery can be considered in well-defined cases of unilateral and bilateral Wilms tumors, but the surgical procedure can be very challenging for the pediatric surgeon to perform.

OBJECTIVE

To assess the added value of personalized 3-dimensional (3-D) kidney models derived from conventional imaging data to enhance preoperative surgical planning.

DESIGN, SETTING, AND PARTICIPANTS

In a survey study, the conventional imaging data of 10 Dutch children with Wilms tumors were converted to 3-D prints and augmented reality (AR) holograms and a panel of pediatric oncology surgeons (n = 7) assessed the quality of the different imaging methods during preoperative evaluation. Kidney models were created with 3-D printing and AR using a mixed reality headset for visualization.

MAIN OUTCOMES AND MEASURES

Differences in the assessment of 4 anatomical structures (tumor, arteries, veins, and urinary collecting structures) using questionnaires. A Likert scale measured differences between the imaging methods, with scores ranging from 1 (completely disagree) to 5 (completely agree).

RESULTS

Of the 10 patients, 7 were girls, and the mean (SD) age was 3.7 (1.7) years. Compared with conventional imaging, the 3-D print and the AR hologram models were evaluated by the surgeons to be superior for all anatomical structures: tumor (median scores for conventional imaging, 4.07; interquartile range [IQR], 3.62-4.15 vs 3-D print, 4.67; IQR, 4.14-4.71; P = .008 and AR hologram, 4.71; IQR, 4.26-4.75; P = .002); arteries (conventional imaging, 3.62; IQR, 3.43-3.93 vs 3-D print, 4.54; IQR, 4.32-4.71; P = .002 and AR hologram, 4.83; IQR, 4.64-4.86; P < .001), veins (conventional imaging, 3.46; IQR 3.39-3.62 vs 3-D print, 4.50; IQR, 4.39-4.68; P < .001 and AR hologram, 4.83; IQR, 4.71-4.86; P < .001), and urinary collecting structures (conventional imaging, 2.76; IQR, 2.42-3.00 vs 3-D print, 3.86; IQR, 3.64-4.39; P < .001 and AR hologram, 4.00; IQR, 3.93-4.58; P < .001). There were no differences in anatomical assessment between the two 3-D techniques (the 3-D print and AR hologram).

CONCLUSIONS AND RELEVANCE

In this study, the 3-D kidney models were associated with improved anatomical understanding among the surgeons and can be helpful in future preoperative planning of nephron-sparing surgery for Wilms tumors. These models may be considered as a supplementary visualization in clinical care.

Mono, bi- and tri-exponential diffusion MRI modelling for renal solid masses and comparison with histopathological findings

PURPOSE

To compare diffusion tensor imaging (DTI), intravoxel incoherent motion (IVIM), and tri-exponential models of the diffusion magnetic resonance imaging (MRI) signal for the characterization of renal lesions in relationship to histopathological findings.

METHODS

Sixteen patients planned to undergo nephrectomy for kidney tumour were scanned before surgery at 3 T magnetic resonance imaging (MRI), with T2-weighted imaging, DTI and diffusion weighted imaging (DWI) using ten b-values. DTI parameters (mean diffusivity [MD] and fractional anisotropy [FA]) were obtained by iterative weighted linear least squared fitting of the DTI data and bi-, and tri-exponential fit parameters (Dbi, fstar,and Dtri, ffast,finterm) using a nonlinear fit of the multiple b-value DWI data. Average parameters were calculated for regions of interest, selecting the lesions and healthy kidney tissue. Tumour type and specificities were determined after surgery by histological examination. Mean parameter values of healthy tissue and solid lesions were compared using a Wilcoxon-signed ranked test and MANOVA.

RESULTS

Thirteen solid lesions (nine clear cell carcinomas, two papillary renal cell carcinoma, one haemangioma and one oncocytoma) and four cysts were included. The mean MD of solid lesions are significantly (p < 0.05) lower than healthy cortex and medulla, (1.94 ± 0.32*10- 3 mm2/s versus 2.16 ± 0.12*10- 3 mm2/s and 2.21 ± 0.14*10- 3 mm2/s, respectively) whereas ffast is significantly higher (7.30 ± 3.29% versus 4.14 ± 1.92% and 4.57 ± 1.74%) and finterm is significantly lower (18.7 ± 5.02% versus 28.8 ± 5.09% and 26.4 ± 6.65%). Diffusion coefficients were high (≥2.0*10- 3 mm2/s for MD, 1.90*10- 3 mm2/s for Dbi and 1.6*10- 3 mm2/s for Dtri) in cc-RCCs with cystic structures and/or haemorrhaging and low (≤1.80*10- 3 mm2/s for MD, 1.40*10- 3 mm2/s for Dbi and 1.05*10- 3 mm2/s for Dtri) in tumours with necrosis or sarcomatoid differentiation.

CONCLUSION

Parameters derived from a two- or three-component fit of the diffusion signal are sensitive to histopathological features of kidney lesions.

Staging and following common pediatric malignancies: MRI versus CT versus functional imaging

Most pediatric malignancies require some form of cross-sectional imaging, either for staging or response assessment. The majority of these are solid tumors and this review addresses the role of MRI, as well as other cross-sectional and functional imaging techniques, for evaluating the most common pediatric solid tumors. The primary emphasis is on neuroblastoma, hepatoblastoma and Wilms tumor, three of the most common non-central-nervous-system (CNS) pediatric solid tumors encountered in young children. The initial focus will be a review of the imaging techniques and approaches used for diagnosis, staging and early post-treatment response assessment, followed by a discussion of the role surveillance imaging plays in pediatric oncology and a brief review of other emerging imaging techniques. The lessons learned here can be applied to most other pediatric tumors, including rhabdomyosarcoma, Ewing sarcoma and osteosarcoma, as well as germ cell tumors, neurofibromatosis and other rare tumors. Although lymphoma, in particular Hodgkin lymphoma, represents one of the more common pediatric malignancies, this is not discussed in detail here. Rather, many of the lessons that we have learned from lymphoma, specifically with regard to how we integrate both anatomical imaging and functional imaging techniques, is applied to the discussion of the other pediatric solid tumors.