Data set for reporting paediatric renal tumours: recommendations from the international collaboration on cancer reporting (ICCR)

Abstract

Tumours arising within the developing kidney of children vary widely in their histological appearance and outcome; optimal therapy requires accurate classification and staging. The two major paediatric cooperative groups provide different therapeutic protocols based on different staging and classification, initially developed to serve patients in North America and Europe, but also used in many other parts/regions of the world. The International Collaboration on Cancer Reporting (ICCR) has developed a structure whereby such complex information may be harmonised, and able to be applied to patients globally. An international expert panel consisting of paediatric pathologists and oncologists produced a set of items critical to cancer reporting and subjected these to review and discussion using the structured processes provided by the ICCR. A formal ICCR structure was assembled, and consensus surrounding elements and their application to different therapeutic protocols was developed. The data set underwent open international consultation. This resulted in the first international data set for Wilms tumour (WT) and other paediatric renal tumours, provided herein. The use of ICCR methods enables a full understanding of highly complex and often overlapping reporting elements by international experts, and the potential of developing a set of commonly applied data elements that are fully defined. This sets the groundwork for future consolidation of definitions and harmonisation of therapies for WT and other paediatric renal tumour patients. It also allows institutions outside the major paediatric cooperative groups to provide therapy based on known elements.

Keywords: ICCR guidelines; Wilms tumours; checklist; data set; paediatric renal tumours; protocol; structured report; synoptic report.

Figure 1

Favourable histology Wilms tumour. By far the most common paediatric renal tumour, Wilms tumour may show a variety of histological patterns, including blastema (undifferentiated), epithelial and stromal. Further, the epithelial and stromal components may also show heterologous differentiation, including mucinous, muscle and adipose differentiation, among others. The tumour in this figure illustrates epithelial and blastemal components.

Figure 2

Anaplastic Wilms tumour: demonstrated are the enlarged, polyploid mitotic figures and marked nuclear enlargement with hyperchromasia that define anaplastic Wilms tumours. These are often subcategorised as focal or diffuse, depending upon the extent of anaplasia.

Figure 3

Nephrogenic rest: many Wilms tumours arise within precursor lesions known as nephrogenic rests. Like Wilms tumours, nephrogenic rests may vary from proliferative to regressing. Experts have distinguished between intralobar and perilobar nephrogenic rests based on the position in the renal lobe, the presence or absence of sharp demarcation and the cellular composition. Illustrated is a sharply demarcated perilobar nephrogenic rest composed of epithelial tubules.

Figure 4

Rhabdoid tumour of kidney: this highly malignant tumour, most commonly occurring in infancy, is composed of a monomorphic population of large cells with vesicular nuclei, often with prominent and large nucleoli, and a large cytoplasmic inclusion composed of intermediate filaments.

Figure 5

Clear cell sarcoma of kidney: these mesenchymal neoplasms show a wide spectrum of histological appearances, and often mimic Wilms tumours as well as other childhood neoplasms. Features distinguishing CCSK from Wilms tumour include a fine, open chromatin pattern, low mitotic rate and a subtly infiltrative border, with entrapment of native renal elements, as seen in the centre of this figure.

Figure 6

Congenital mesoblastic nephroma: these stromal neoplasms present most commonly in infancy and may be composed of plump, variably spindled cells (classified as the cellular subtype, illustrated in this figure), or may be composed of markedly elongated, interdigitating cells (classified as the classic subtype).