Diagnostic magnetic resonance imaging characteristics of congenital mesoblastic nephroma: a retrospective multi-center International Society of Pediatric Oncology-Renal Tumor Study Group (SIOP-RTSG) radiology panel study.

BACKGROUND: Congenital mesoblastic nephroma is the most common solid renal tumor in neonates. Therefore, patients <3 months of age are advised to undergo upfront nephrectomy, whereas invasive procedures at diagnosis in patients ≥3 months of age are discouraged by the International Society of Pediatric Oncology-Renal Tumor Study Group (SIOP-RTSG). Nevertheless, discriminating congenital mesoblastic nephroma, especially from the more common Wilms tumor, solely based on imaging remains difficult. Recently, magnetic resonance imaging (MRI) has become the preferred modality. Studies focusing on MRI characteristics of congenital mesoblastic nephroma are limited. OBJECTIVE: This study aims to identify diagnostic MRI characteristics of congenital mesoblastic nephroma in the largest series of patients to date. MATERIALS AND METHODS: In this retrospective multicenter study, five SIOP-RTSG national review radiologists identified 52 diagnostic MRIs of histologically proven congenital mesoblastic nephromas. MRI was performed following SIOP-RTSG protocols, while radiologists assessed their national cases using a validated case report form. RESULTS: Patients (24/52 classic, 11/52 cellular, and 15/52 mixed type congenital mesoblastic nephroma, 2/52 unknown) had a median age of 1 month (range 1 day-3 months). Classic type congenital mesoblastic nephroma appeared homogeneous with a lack of hemorrhage, necrosis and/or cysts, showing a concentric ring sign in 14 (58.3%) patients. Cellular and mixed type congenital mesoblastic nephroma appeared more heterogeneous and were larger (311.6 and 174.2 cm3, respectively, versus 41.0 cm3 for the classic type (P<0.001)). All cases were predominantly T2-weighted isointense and T1-weighted hypointense, and mean overall apparent diffusion coefficient values ranged from 1.05-1.10×10-3 mm2/s. CONCLUSION: This retrospective international collaborative study showed classic type congenital mesoblastic nephroma predominantly presented as a homogeneous T2-weighted isointense mass with a typical concentric ring sign, whereas the cellular type appeared more heterogeneous. Future studies may use identified MRI characteristic of congenital mesoblastic nephroma for validation and for exploring the discriminative non-invasive value of MRI, especially from Wilms tumor.

Laparoscopic strategies in complex upper urinary tract obstruction.

OBJECTIVES: We enumerate the various laparoscopic strategies to resolve upper urinary tract (UUT) obstruction in the context of variations in anatomy and report their outcomes. PATIENTS AND METHODS: Retrospective review of primary laparoscopic UUT reconstructions performed between May 2012 and May 2021. Anomalies included: malrotated kidney (MRK), horseshoe kidney (HSK), duplex kidney (DK), pure intrarenal pelvis (IRP) and mid-ureteric stenosis (MUS). Success was defined by postoperative resolution of symptoms, improvement of anterior-posterior renal pelvic diameter (APD) on US and drainage on Mag3. Complications were categorised by Clavien-Dindo grading. Outcomes compared using the student's t-test with P < 0.05 considered statistically significant. RESULTS: Of the 214 laparoscopic primary UUT reconstructions, 37 (17.2 %) were: 13-MRK, 12-HSK, 4-DK, 4-IRP and 4-MUS. Median age at surgery was 5-years (range 0.3-15). Dismembered pyeloplasty: 8; pyeloplasty with renal sinus dissection: 8; neo-PUJ anastomosis: 8; primary ureterocalycostomy: 7; pyeloureterostomy: 2; and uretero-ureterostomy: 4. Median follow-up was 43-months (range 8-108) with a success rate of 94.5 % (35/37). Complete resolution of symptoms in 20/21 patients; improvement of hydronephrosis on US in 35/37 patients (median pre-operative APD 27 mm vs. median postoperative APD 8 mm) [P < 0.001]; improvement of drainage on diuretic renogram in 32/34 kidneys and stable/improved DRF in 34/35 kidneys (median preoperative DRF - 45 % vs. median postoperative DRF - 47 %) [P > 0.05]. Postoperative complications managed medically (II Clavien) included urinary tract infections - 2 patients (5 %), stent-related symptoms in 2 (5 %) and umbilical port site collection in 1 patient (3 %). Recurrent pelvi-ureteric junction obstruction PUJO occurred in one patient (3 %) requiring redo surgery (IIIb Clavien), renal stones in 1 (3 %) which resolved with ESWL (IIIb Clavien); in 1 (3 %) patient with a HSK there was complete loss of ipsilateral kidney function but this was managed conservatively up to date (I Clavien). CONCLUSION: Laparoscopic transperitoneal approach allows the prompt recognition of in-situ anatomical variants. UUT obstruction in such settings calls for a variety of strategies with excellent outcomes.

Surgical management, staging, and outcomes of Wilms tumours with intravascular extension: Results of the IMPORT study.

PURPOSE: To review surgical management, tumour stage and clinical outcomes in children with intravascular extension of Wilms tumour (WT) registered in a national clinical study (2012-19). METHODS: WTs with presence/suspicion of tumour thrombus in the renal vein (RV) or beyond on radiology, surgery or pathology case report forms were identified. Only cases where thrombus was confirmed by surgeon and/or reference pathologist were included. Surgical management, disease stage, overall (OS) and event free survival (EFS) were investigated. RESULTS: 69/583 (11.8%) patients met the inclusion criteria. Forty-six (67%) had abdominal stage III due to thrombus-related reasons: 11 had macroscopically incomplete resection, including 8 cases where cavotomy was not performed; 20 had piecemeal complete resection of thrombus; 15 had microscopically positive resection margins at the RV. 66% of tumour thrombi contained viable tumour. There were eight relapses and five deaths. EFS, but not OS, was significantly associated with completeness of surgical resection (P<0.05). OS and EFS were also significantly associated with histological risk group (P<0.05) but not with viability of tumour thrombus (P=0.19; P=0.59). CONCLUSIONS: WTs with intravascular extension have a high risk of local stage III due to thrombus-related reasons. Controlled complete removal of the thrombus should be the aim of surgery. LEVEL OF EVIDENCE: Level II.

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.

Pediatric and young adult renal cell carcinoma.

Renal cell carcinoma (RCC) is rare in children but is the most common renal tumor in adults. Pediatric RCC has different clinical characteristics, histopathology, and treatment compared with adult disease. Databases were reviewed from inception to February 2020, identifying 32 publications pertaining to 350 patients under 27 years. Surgery is the cornerstone for cure in localized RCC. Lymph node dissection remains controversial. Conventional radiotherapy has no curative role in RCC; similarly, conventional chemotherapy has not proven to be effective in large cohorts. Pediatric metastatic RCC has a poor outlook. There are no published prospective studies demonstrating which adjuvant therapy could improve outcome. Sunitinib, a tyrosine kinase inhibitor, is recommended in this group despite limited evidence. This review provides an overview for pediatric RCC, including the evolving role of precision medicine.

Characteristics and Outcome of Children with Renal Cell Carcinoma: A Narrative Review.

Pediatric renal cell carcinoma (RCC) is a rare type of kidney cancer, most commonly occurring in teenagers and young adolescents. Few relatively large series of pediatric RCC have been reported. Knowledge of clinical characteristics, outcome and treatment strategies are often based on the more frequently occurring adult types of RCC. However, published pediatric data suggest that clinical, molecular and histological characteristics of pediatric RCC differ from adult RCC. This paper summarizes reported series consisting of ≥10 RCC pediatric patients in order to create an up-to-date overview of the clinical and histopathological characteristics, treatment and outcome of pediatric RCC patients.

Wilms tumors and their precursors: Radiological diagnosis versus histology.

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.