Paediatric renal tumours comprise a different spectrum of entities than occur in adults, reflecting the distinct chromatin state in the developing child. Nephroblastoma (Wilms tumour) with its histology of ‘nephrogenesis gone awry’ belongs to the primitive visceral cancers of childhood and is rare in adulthood, but makes up 90% of paediatric renal malignancies. Amongst paediatric renal neoplasms are some of the most aggressive and treatment-resistant cancers, including malignant rhabdoid tumour and renal medullary carcinoma. Recent molecular analysis has recognised that certain tumours arising within the kidney represent the visceral manifestation of a neoplasm that may alternatively arise within soft tissue (malignant rhabdoid tumour of kidney, congenital mesoblastic nephroma and peripheral primitive neuroectodermal tumour). Shared genetic driver mutations have been identified in what may appear to be very different tumours, but which have shared histology. This is true of the so-called BCOR family of tumours, whereby a BCOR rearrangement, or uncommonly instead the gene fusion YWHAE-NUTM2, occurs in clear cell sarcoma of kidney but also in high-grade endometrial stromal sarcoma and primitive mixed mesenchymal tumour of infancy. Dysregulation of chromatin is the oncogenic driver of some of these rare aggressive paediatric kidney cancers, including peripheral neuroectodermal tumour, clear cell sarcoma of kidney and malignant rhabdoid tumour.