Lymph node imaging of pediatric renal and suprarenal malignancies

How we approach paediatric renal tumour core needle biopsy in the setting of preoperative chemotherapy: A Review from the SIOP Renal Tumour Study Group

The International Society of Paediatric Oncology Renal Tumour Study Group (SIOP-RTSG) advocate treating children with Wilms tumour (WT) with preoperative chemotherapy, whereas the Renal Tumor Committee of the Children's Oncology Group (COG) advocates primary nephrectomy (without biopsy) when feasible. Successive SIOP-RTSG trial protocols recommended pretreatment biopsy of children with unilateral tumours only where there were features to suggest an increased probability of a non-WT requiring a change in management. The UK experience in the SIOP WT 2001 trial showed that an alternate approach of performing biopsies on all children with renal tumour masses to determine histology at diagnosis rarely changes management, and can result in misdiagnosis (particularly patients in the age range typical for WT). Although a more selective approach to biopsy has been routine practice in all other countries participating in SIOP-RTSG trials, there was variation between national groups. To address this variation and provide evidence-based recommendations for the indications and recommended approach to renal tumour biopsy within the SIOP paradigm, an international, multidisciplinary working group of SIOP-RTSG members was convened. We describe the resulting recommendations of this group, which are to be incorporated in the ongoing SIOP-RTSG UMBRELLA study.

[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.

Retroperitoneal and Pelvic Lymph Nodes in Children: What Is Normal?

OBJECTIVE. The purpose of this study was to evaluate size criteria for retroperitoneal and pelvic lymph nodes in healthy children. MATERIALS AND METHODS. We identified all trauma patients younger than 18 years old without underlying disease and with CT scans without abnormalities in the abdomen and pelvis during 2014-2015. Two pediatric radiologists reviewed the studies independently and recorded the number of retroperitoneal and pelvic lymph nodes with a long diameter 5 mm or greater and the size (two perpendicular diameters) of the largest lymph node in five anatomic locations. Discrepant results were reviewed in consensus. The relationship of short diameter to age and interobserver variability was evaluated. RESULTS. A total of 166 patients (86 boys) with a mean age of 7.2 years old (range, 0.1-18.0 years old) were identified. More than 95% of lymph nodes in the retroperitoneum and pelvis had a short diameter measuring at most 7 and 8 mm, respectively, by consensus. The size of the largest short diameter of lymph nodes did not vary with age. More than four lymph nodes were identified in any anatomic location in only three patients, by only one of the radiologists. Agreement for lymph nodes with largest diameter of 5 mm or greater between radiologists ranged from 70.5% to 97.6% for the five anatomic locations with poor interobserver agreement (κ, 0.2-0.3). CONCLUSION. The size and number of retroperitoneal and pelvic lymph nodes in children are less than in adults. A short diameter threshold of 7 mm (retroperitoneal) and 8 mm (pelvic) and more than four lymph nodes with long diameter of 5 mm or greater in one location may define disease.