From Wilms to kidney tumors: which ones require a biopsy?

Ninety percent of childhood renal tumors are Wilms tumors (nephroblastoma). While the Children's Oncology Group (COG) recommends primary surgery, the International Society of Paediatric Oncology (SIOP) recommends neoadjuvant chemotherapy, which can be initiated without histological confirmation if the presentation is typical for Wilms tumor. This review article describes the clinical, biological and radiologic criteria used by the SIOP community to consider diagnostic biopsy, i.e. when the renal origin is doubtful, when a pseudotumor is suspected or when a non-Wilms histology may be anticipated.