Paediatric renal tumours: recent developments, new entities and pathological features.

Paediatric renal tumours represent a relatively common group of childhood solid neoplasms, in which both diagnosis and treatment are highly dependent on the histopathological findings. In addition to Wilms' tumour (nephroblastoma), a number of specific distinct entities are now reported, including (congenital) mesoblastic nephroma, clear cell sarcoma of the kidney, rhabdoid tumour of the kidney, specific paediatric variants of renal cell carcinoma, and others such as renal primitive neuroectodermal tumour and desmoplastic small round cell tumour. Recent advances in both molecular biological findings and immunohistochemistry allow reliable diagnosis of most of these entities even on the basis of small needle biopsy specimens. This review highlights both the salient features important for the diagnostic pathologist reporting such cases, and areas in which either new classifications or major advances in diagnostic criteria have occurred in recent years.